unit 1. frequency distribution
TRANSCRIPT
UNIT 1. FREQUENCY DISTRIBUTION BY PROF. SWATI BHALERAO
FY BBA (Sem 2) – 205 – Business Statistics – Patten 2019
SYLLABUS
• 1.1 Raw data, variable, discrete variable, continuous variable, constant, attribute with illustration.
• 1.2 Classification- Concept and definition of classification, objectives of classification, types of
• classification.
• 1.3 Frequency Distribution- Discrete and Continuous frequency distribution, Cumulative frequency
• and Cumulative frequency distribution.
• 1.4 Graphs & Diagram- Histogram, Ogive curve, Pie-Diagram, Bar Diagram, Multiple bar Diagram,
• Sub-divided bar diagram
DATA
• Data consist of information coming from observations, counts, measurement or
responses.
• It is a term given to raw facts or figures, which alone are of little value. Data represent
something, like body weight, the name of a village, the age of a child, the temperature
outside, etc.
• Qualitative data consist of labels, features, nonnumeric entries. Quantitative data consist
of numerical measurements of counts and numbers used for calculations
POPULATION AND SAMPLE
• The word population in statistics means the totality of the set of objects under study. It
should not be understood in the limited sense in which it is generally used to mean
people in a certain city or country.
• A sample is a selected number of entities or individuals which form a part of the
population under study. The study of a sample is more practical and economical in most
situations where the population is large and is used to make conclusions about the entire
population.
VARIABLES AND ATTRIBUTES
• In statistics characteristics are of two types. Measurable and non-measurable.
Measurable characteristics are those that can be quantified as expressed in numerical
terms. The measurable characteristics are known as variables. A non-measurable
characteristic is qualitative in nature and cannot be quantified. Such a characteristic e.g
nationality, religion, etc are called as attributes.
TYPES OF VARIABLE
• Discrete or categorical variables are those numeric or nominal variables that take a
finite, limited, countable number of possibilities or values (e.g. number of children in
families). They come in chunks that cannot be reduced. Discrete/categorical variables
can be further categorized as either nominal or ordinal variable
• Example of discrete variables: Sex or gender, type of building, livelihood zone, school
grade, province name, number of people, etc.
• Continuous variables are variables that have an infinite or not countable number of
value possibilities. There always exists a third value between any two values on it. This
includes values for which numerous decimal places can be used. A continuous variable
can be transformed into categories and become a discrete variable. Continuous
variables can be further categorized as either interval or ratio variables.
• Example of continuous variables: Time, weight, height, income, age, distance, quantity
of milk produced, cultivated area, etc.
CLASSIFICATION
• Classification is the process of arranging the data under various understandable homogeneous
groups for the purpose of convenient interpretation. The grouping of data is make on the basis
of common characteristics
• Objectives of classification
1. To facilitate comparison
2. To study the relationship
3. To trace location of important facts at a glance
4. To eliminate unnecessary details
5. To effect statistical treatment of the collected data
6. To facilitate easy interpretation
• Significance of classification
1. It is helpful to tabulation
2. It leads to a valid result
3. It makes interpretation clear and meaningful
TYPES OF CLASSIFICATION.
• Geographical Classification
• In this type the data are classified on the basis of geographical locational differences among various items on
the basis of states districts, cities, regions, and the like
• Chronological Classification
• Under this type data are classified in them basis of differences in time or period such as rainfall for 12 months.
• Qualitative Classification
• In this classification, data are classified on the basis of some attributes or qualitative phenomena such as
religion, sex, marital status, literacy, occupation and the like.
• Quantitative Classification
• Under this type data are classified according to some quantitative phenomena capable of quantitative
measurement such as age, experience, income, prices, production, sales and the like
FREQUENCY DISTRIBUTION
• Frequency distribution is the process or method in simplify mass of data into grouped form of
classes and the member of items in such class is recorded
• a. Univaraite Frequency Distribution b. Bivariate Frequency Distribution
• a. Univariate Frequency distribution
• It is one way frequency single variable distribution and further classification into
• 1.Individual Observation 2. Discrete Frequency Distribution 3. Continuous Frequency
Distribution
• b. Bivariate Frequency Distribution
• Bivariate Frequency Distribution is a two way Frequency distribution, where two variables are
measured in the same set of items through cross distribution
1) DISCRETE FREQUENCY DISTRIBUTION
• In discrete frequency distribution, values of the variable is arranged individually. The
frequencies of the various values are the number of times each value occurs.
Ex. The weekly wages in Rs. paid to the workers are given below. Form a discrete frequency
distribution
300,240,240.150,120,240,120,120,150,150,150,240,150,150,120,300,120,150,240,150,150,1
20,240,150,240,150,120,120,240,150.
SOLUTION
Weekly wages in
Rs.(x)
Tally marks No. of workers
120 ⫵ III 8
150 ⫵⫵ II 12
240 ⫵III 8
300 II 2
Weekly wages in Rs.(x) 120 150 240 300 Total
No. of workers(frequncies) 8 12 8 2 30
CONTINUOUS FREQUENCY DISTRIBUTION
Continuous frequency distribution is also known as grouped frequency distribution. This is a form in
which class intervals and respective class frequencies are given
We can find frequency distribution by the following steps:
1. Find the smaller and largest observation. Calculate the difference between them. This difference is called
as range.
2. Next, divide the Decide the classes, by dividing the range into several intervals. The number of classes be
preferred between 7 to 20.
3. Prepare the first column of table by entering the class intervals
4. Classify the observation one by one in the appropriate class by putting tally marks in the second column
against the corresponding class. Cross the observation from the original data to avoid double counting.
5. Count the tally marks and enter the number in the third column.
EXAMPLES OF
• Let us consider the following example regarding daily maximum temperatures in in
• a city for 50 days.
• 28, 28, 31, 29, 35, 33, 28, 31, 34, 29,
• 25, 27, 29, 33, 30, 31, 32, 26, 26, 21,
• 21, 20, 22, 24, 28, 30, 34, 33, 35, 29,
• 23, 21, 20, 19, 19, 18, 19, 17, 20, 19,
• 18, 18, 19, 27, 17, 18, 20, 21, 18, 19.
SOLUTION
• Minimum Value= 17 Maximum Value=35 Range=35-17=18
• Number of classes=5 (say) width of each class=4
• Table Showing frequency distribution of temperature in a city for 50 days.
Class Intervals (Temperatures in ) Frequency
17-21 17
21-25 7
25-29 10
29-33 9
33-37 7
Total 50
TERMS USED IN THE FREQUENCY DISTRIBUTION
• Class Limits
• The class limits are the lowest and the highest values but can be included in the class
• Class Frequency
• The number of items included or counted in each of the classes is called class Frequency
• Mid-point
• Mid-point in their value lying half way between the lower and upper limits of a class
interval
TERMS USED IN THE FREQUENCY DISTRIBUTION
• Class limits. There are two for each class.
The lower class limit of a class is the smallest data value that can go into the class.
The upper class limit of a class is the largest data value that can go into the class.
Class limits have the same accuracy as the data values; the same number of decimal places as the data values.
• Class boundaries. They are halfway points that separate the classes.
The lower class boundary of a given class is obtained by averaging the upper limit of the previous class and the
lower limit of the given class.
The upper class boundary of a given class is obtained by averaging the upper limit of the class and the lower limit
of the next class.
Open-ended classes are classes that do not have either an upper limit or a lower limit.
METHOD OF CLASSIFICATION OF DATA
• Exclusive Method : This method is useful whether the value is complete number or in
decimals. In case of exclusive series, value of the upper limit of a class is included in the
lower limit of the next class interval. Value of the upper limit of the class is included in
that very class interval.
• Inclusive Method : In inclusive series value of the upper limit of a class is included in
that very class interval. Inclusive series is useful when value is incomplete number.
CUMULATIVE FREQUENCY DISTRIBUTION
• There are two kinds of cumulative frequency distribution. i) Less than cumulative frequency
distribution and ii) More than cumulative frequency distribution
• i) Less than cumulative frequency distribution
Frequency distribution both discrete and continuous are to be taken in ascending order.
The total of the frequencies from the beginning up to and including each frequency is found.
That cumulative frequency shows how many items are less than or equal to the corresponding
value of the class interval.
• ii) More than cumulative frequency distribution:
Frequency distribution both discrete and continuous are to be taken in ascending order.
The total of the frequencies from the end up to and including each frequency is found. That
cumulative frequency shows how many items are more than or equal to the corresponding
value of the class interval.
EXAMPLES
• For the following distribution find (i) less than cumulative frequencies and (ii) More than
cumulative frequencies
Marks Frequencies
0 – 10 5
10 – 20 12
20 – 30 15
30 – 40 4
40 – 50 4
RELATIVE FREQUENCIES
• The proportion of number of observations in a class is the relative frequency.
• Relative Frequency = Class Frequency / Total Frequency
GRAPHS & DIAGRAM
• The various graphs associated with frequency distribution.
• Graphs are charts consisting of points, lines and curves. Charts are drawn on graph sheets.
Suitable scales are to be chosen for both x and y axes, so that the entire data can be
presented in the graph sheet. Graphical representations are used for grouped quantitative
data.
• Statistical measures such as quartiles, median and mode can be found from the appropriate
graph.
• Graphs are useful for analysis of timeseries, regression analysis, business forecasting,
interpolation, extrapolation, and inverse interpolation.
TYPES OF GRAPHS
• Graphs are broadly divided into two
i) Graphs of time series or Historigrams and
ii) Graphs of frequency distribution
• Graphs of frequency distribution is further divided into
a) Frequency lines used to represent discrete frequency distribution
b) Histogram
c) Frequency polygon used to present continuous frequency distribution
d) Frequency curve
e) Ogive curve used to represent cumulative frequency distribution
GRAPHS OF FREQUENCY DISTRIBUTION
• Frequency lines: Are used to represent discrete frequency
distribution. Variable is taken in the X axis and the frequencies
in the Y axis, the pair of points (variable, frequency) is plotted
on the graph. From each point a vertical line is drawn to the X
axis. The resulting graph is the frequency line.
• Weekly wages in Rs. No. of workers
• 120 8
• 150 12
• 240 8
• 300 2
HISTOGRAM
• When the data are classified based on the class intervals it can be represented by a
histogram. Histograms are similar to bar diagram without any gap in between. There is no
gap between the bars, since the classes are continuous. The bars are drawn only in outline
without colouring or marking as in the case of simple bar diagrams. It is the suitable form
to represent a frequency distribution.
• Class intervals are to be presented in x axis and the bases of the bars are the respective
class intervals. Frequencies are to be represented in y axis. The heights of the bars are
equal to the corresponding frequencies.
EXAMPLE
• Draw a Histogram for the following distribution giving the marks obtained by 60 students
of a class in a college .
• Marks : 20-24 25-29 30-34 35-39 40-44 45-49 50-54
• No. of students: 3 5 12 18 14 6 2
• Solution: Here class intervals given are of inclusive type . State the upper limit of a class
is not equal to the lower limit of its following class , the class boundaries will have to
be determined
Marks : 19.5-24.5 24.5-29.5 29.5-34.5 34.5-39.5 39.5-44.5 44.5-49.5 49.5-54.5
No. of 3 5 12 18 14 6 2
Student
scale: x-axis 1 cm. = 10 marks y-axis 1 cm. = 5 students.
FREQUENCY POLYGON AND FREQUENCY CURVE
• It is another method of representing a frequency distribution of a graph. Frequency
polygons are more suitable than histograms whenever two or more frequency
distributions are to be compared.
• Frequency polygon of a grouped or continuous freq. distribution is a straight line graph.
The frequencies of the classes are plotted against the mid-values of the corresponding
classes . The points so obtained are joined by straight lines (segments) to obtain the
frequency polygon.
• Frequency polygon and frequency curves are drawn along with the histogram or
separately,
• The following data show the number of accidents sustained by 313 drivers of a public utility
company over a period of 5 years. Draw the frequency polygon
• No. of accidents : 0 1 2 3 4 5 6 7 8 9 10 11
• No. of drivers : 80 44 68 41 25 20 13 7 5 4 3 2
• Frequency polygon of a number of accidents
• Draw a Histogram & Frequency polygon from the following distribution giving marks of 50 students in
statistics .
• Marks in Statistics : 0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90
• No. of students : 0 2 3 7 13 13 9 2 1
• Note that, here we will first draw Histogram and then the mid-points of the top of bars are joined by
line segments to get the frequency polygon.
FREQUENCY CURVE
• Frequency curve is similar like frequency polygon, only the difference is that the points are
joined by a free hand curve instead of line segments as we join in frequency polygon.
• Let us study the following examples to study the concept of frequency curve .
• Example 10: Draw a frequency curve for the following data :
• Age (yrs) : 17-19 19-21 21-23 23-25 25-27 27-29 29-31
• No. of students : 7 13 24 30 22 15 6
• Solution: Here we will take ages on horizontal axis ( i.e. x-axis ) and no. of students on
vertical axis ( i. e. say y-axis )
• We will plot the given frequencies
(No. of students) against mid-points
of the given class interval & then
join these points by free hand curve.
Extremities (first and the last points
plotted ) are joined to the mid-
points of the neighbouring class
intervals.
• Draw a Histogram & frequency curve for the following data:
• Age (yrs) : 17-19 19-21 21-23 23-25 25-27 27-29 29-31
• No. of students : 7 13 24 30 22 15 6
• Solution: First we will draw histogram & then the mid-points of the top of the bars are
joined by free hand curve to get the frequency curve .
OGIVE OR CUMULATIVE FREQUENCY CURVE
• Ogive is a graphic presentation of the cumulative frequency (c.f) distribution of
continuous variable. It consists in plotting the c.f. (along the y-axis ) against the class
boundaries (along x-axis ) . Since there are two types of c.f. distributions namely ' less
than ' c.f. and 'more than ' c.f. , we have accordingly two types of ogives , namely ,
• i) ' less than and equal to ' ogive ,
• ii) ' more than and equal to' ogive
• 'Less than and equal to ogive : This consists of plotting the 'less than ' cumulative frequencies against the
upper class boundaries of the respective classes . The points so obtained are joined by a smooth free hand
curve to give 'less than ' ogive . Obviously, 'less than ' ogive is an increasing curve , sloping upwards from left
to right .
• Note : Since the frequency below the lower limit of the first class ( i.e. upper limit of the class preceding
the first class ) is zero , the ogive curve should start on the left with a cum. freq. zero of the lower
boundary of the first class .
• ‘More than and equal to’ ogive: This consists of plotting the ' more than ' cum. frequencies against the lower
class boundaries of the respective classes . The points so obtained are joined by a smooth free hand curve
to give ' equal give . Obviously, 'more than ' ogive is a decreasing curve , slopes downwards from left to right
• Note: We may draw both the 'less than' and 'more than and equal to‘ ogives on the same graph . If done so,
they intersect at a point. The foot of the perpendicular from their point of intersection on the x-axis gives
the value of the median .
• Ex. The following table gives the distribution of monthly income of 600 families in a certain city .
• Draw a 'less than ' and a 'more than equal to' ogive curve for the above data on the same graph and from
there read the median income .
• Solution: For drawing the 'less than' and 'more than' equal to ogive we convert the given distribution into
'less than' and 'more than equal to' cumulative frequencies (c.f.) as given in the following table.
Monthly Income Below 75 75-150 150- 225 225- 300 300- 375 375- 450 Above 450
No. of families 60 170 200 60 50 40 20
TYPES OF DIAGRAM
• 1) One dimensional diagrams:
• a) Simple Bar diagrams
• b) Multiple Bar diagrams (joint Bar Diagrams)
• c) Sub-divided Bar Diagram and
• d) Percent Bar Diagrams.
• 2) Two dimensional diagrams: Pie or Circular diagram .
IMPORTANCE
• To understand various trends of the data (which is already classified and tabulated) at a glance
and to facilitate the comparison of various situations, the data are presented in the form of
diagrams & graphs. Diagrams are useful in many ways, some of the uses are given below:-
• i) Diagrams are attractive and impressive.
• ii) Diagrams are useful in simplifying the data.
• iii) Diagrams save time and labour.
• iv) Diagrams are useful in making comparisons.
• v) Diagrams have universal applicability.
SIMPLE BAR DIAGRAM:
• A simple bar chart is used to
represent data involving only one
variable classified on a spatial,
quantitative or temporal basis. In a
simple bar chart, we make bars of
equal width but variable length, i.e.
the magnitude of a quantity is
represented by the height or length
of the bars
MULTIPLE BAR DIAGRAMS:
• The following diagram gives
the figures of Indo-US trade
during 1987 to 1990. The
figures of Indian Exports &
Imports are in billion.
Answer the following
questions from the diagram
given below:
SUB-DIVIDED BAR DIAGRAMS:
• The following diagram shows the
number of Govt. and Non-Govt.
Companies in various years. Study
the diagram and answer the
questions given below:-
PIE-DIAGRAM
• A pie chart is a type of graph
that represents the data in
the circular graph. The slices
of pie show the relative size
of the data. It is a type of
pictorial representation of
data. A pie chart requires a
list of categorical variables
and the numerical variables.
UNIT 2. MEASURE OF CENTRAL TENDENCY
BY PROF. SWATI BHALERAO
FY BBA (Sem 2) – 205 – Business Statistics – Patten 2019
SYLLABUS
• 2.1 Concept and meaning of Measure of Central Tendency, Objectives of Measure of Central
• Tendency, Requirements of good Measure of Central Tendency.
• 2.2 Types of Measure of Central Tendency, Arithmetic Mean (A.M), Median, Mode for discrete
• and Continuous frequency distribution, Merits & Demerits of A.M., Median , Mode,
• Numerical Problem.
• 2.3 Determination of Mode and Median graphically.
• 2.4 Empirical relation between mean, median and mode.
• 2.5. Combined Mean
• 2.6. Numerical Problems.
INTRODUCTION
• There is a tendency in almost every statistical data that most of the values concentrate at
the centre which is referred as “central tendency‘. The typical values which measure the
central tendency are called measures of central tendency. Measures of central tendency
are commonly known as ‘Averages.‘ They are also known as first order measures.
Averages always lie between the lowest and the lightest observation.
• The purpose for computing an average value for a set of observations is to obtain a single
value which is representative of all the items and which the mind can grasp simply and
quickly. The single value is the point or location around which the individual items cluster.
TYPES OF AVERAGES
• The following are the five types of averages which are commonly used in practice.
• 1. Arithmetic Mean or Mean (A.M)
• 2. Median
• 3. Mode
• 4. Geometric Mean (G.M)
• 5. Harmonic Mean (H.M)
• Of these, arithmetic mean, geometric mean and harmonic mean are called mathematical
averages; median and mode are called positional averages. Here we shall discuss only the first
three of them in detail, one by one.
ARITHMETIC MEAN (A.M)
• (i) For Simple or Ungrouped data:(where frequencies are not given) Arithmetic Mean is
defined as the sum of all the observations divided by the total number of observations in
the data and is denoted by x , which is read as ‗x-bar‘
• In general, if x1 x2……., xn are the n observations of variable x, then the arithmetic
mean is given by
• If we denote the sum x1 + x2 +………………+x n as ∑x , then
• Note: The symbol ∑ is the Greek letter capital sigma and is used in Mathematics to
denote the sum of the values.
• Steps: (i) Add together all the values of the variable x and obtain the total, i.e, ∑x.
• (ii) Divide this total by the number of observations.
GROUPED DATA (CLASS INTERVALS AND FREQUENCIES ARE GIVEN )
• Formula where N = ƒ and x = Mid-point of the class intervals
• Steps : (1) Obtain the mid-point of each class interval
• ( Mid-point = lower limit + upper limit ) / 2
• (2) Multiply these mid-points by the respective frequency of each class interval and
obtain the total ∑fx.
• (3) Divide the total obtained by step (2) by the total frequency N.
EXAMPLE
• 1. Find the arithmetic mean for the following data representing marks in six subjects at the
H.S.C examination of a student. (80.83)
• 2. Find arithmetic mean for the following data . 425 , 408 , 441 , 435 , 418
• 3. Calculate arithmetic mean for the following data . (13.83 Years)
Age in years: 11 12 13 14 15 16 17
No . of Students: 7 10 16 12 8 11 5
• 4. Find the arithmetic mean for the following data representing marks of 60 students. (37.83)
Marks 10-20 20-30 30-40 40-50 50-60 60-70 70-80
No. of Students 8 15 13 10 7 4 3
• Solution: The class intervals are of inclusive type. We first make them continuous by
finding the class boundaries. 0.5 is added to the upper class limits and 0.5 is subtracted
from the lower class limits to obtain the class boundaries as
• 130-0.5= 129.5 and 134+0.5=134.5
• 135-0.5= 134.5 and 139+0.5= 139.5 and so on.
• 6. Calculate the arithmetic mean of heights of 80 Students for the following data.
• Heights in cms
• 130- 134 135- 139 140- 144 145- 149 150- 154 155- 159 160- 164
• No. of Students
• 7 11 15 21 16 6 4
MERITS AND DEMERITS OF ARITHMETIC MEAN
• Merits of Arithmetic Mean .
• (1) It is rigidly defined .
• (2) It is easy to understand and easy to calculate .
• (3) It is based on each and every observation of the series .
• (4) It is capable for further mathematical treatment .
• (5) It is least affected by sampling fluctuations.
• Demerits of Arithmetic Mean .
• (1) It is very much affected by extreme observations.
• (2) It can not be used in case of open end classes.
• (3) It can not be determined by inspection nor it can be located graphically.
• (4) It can not be obtained if a single observation is missing .
• (5) It is a value which may not be present in the data .
MEDIAN
• The median by definition refers to the middle value in a distribution. Median is the value
of the variable which divides the distribution into two equal parts. The 50% observations
lie below the value of the median and 50% observations lie above it. Median is called a
positional average. Median is denoted by M.
• (i) For Simple data or ungrouped data: Median is defined as the value of the middle item
of a series when the observations have been arranged in ascending or descending order
of magnitude.
• Steps: 1) Arrange the data in ascending or descending order of magnitude.
• (Both arrangements would give the same answer).
• 2) When n is odd:
• Median= value of term
• 3 ) When n is even:
• Median= Arithmetic Mean of value of terms.
• i.e, adding the two middle values and divided by two. where n = number of observations
FOR UNGROUPED FREQUENCY DISTRIBUTION:
• Steps:
• 1) Arrange the data in ascending or descending order of magnitude with respective
frequencies .
• 2) Find the cumulative frequency (c. ƒ) less than type .
• 3) Find N/2 , N = total frequency.
• 4) See the c. ƒ column either equal or greater than N/2 and determine the value of the
variable corresponding to it . That gives the value of Median .
FOR GROUPED DATA.
• Steps:
• 1) Find the c.f less than type
• 2) Find N/2, N= total frequency.
• 3) See the c.f column just greater than
N/2.
• 4) The Corresponding class interval is
called the Median class.
• 5) To find Median, use the following
formula
FOR GROUPED DATA (OR) DISCRETE DATA
• For Grouped data (or) discrete data: (values and frequencies are given )
• If x1, x2 …… xn are the values of the variable x with corresponding frequencies ƒ1, ƒ2,
………ƒn then the arithmetic mean of x is given by
• Steps :
• (1) Multiply the frequency of each row with the
variable x and obtain the total ∑fx.
• (2) Divide the total ∑fx by the total frequency.
EXAMPLE
• 1. Find the median for the following set of observations 65, 38, 79, 85, 54, 47, 72 (65 units)
• 2. Find the median for the following data. 25, 98, 67, 18, 45, 83, 76, 35 (56 Units)
• 3. From the following data find the value of Median. (3000)
• Income in Rs: 1500 2500 3000 3500 4500
• No. of persons 12 8 15 6 5
• 4.The following data relate to the number of patients visiting a government hospital daily:
No. of patients : 1000- 1200 1200- 1400 1400- 1600 1600- 1800 1800- 2000 2000- 2200
No. of days : 15 21 24 18 12 10
MERITS OF DEMERITS MEDIAN
• 1. It is rigidly defined .
• 2. It is easy to understand and easy to calculate .
• 3. It is not affected by extreme observations as it is a positional average.
• 4. It can be calculated , even if the extreme values are not known .
• 5. It can be located by mere inspection and can also be located graphically.
• 6. It is the only average to be used while dealing with qualitative characteristics which
can not be measured numerically .
• Demerits of Median :
• 1. It is not a good representative in many cases.
• 2. It is not based on all observations.
• 3. It is not capable of further mathematical treatment .
• 4. It is affected by sampling fluctuations.
• 5. For continuous data case , the formula is obtained on the assumption of uniform
distribution of frequencies over the class intervals. This assumption may not be true.
MODE
• (i) For Raw data:
• Mode is the value which occurs most frequently ,in a set of observations. It is a value which is
repeated maximum number of times and is denoted by Z.
• (ii) For ungrouped frequency distribution:
• Mode is the value of the variable corresponding to the highest frequency.
• (iii) For Grouped data:
• In a Continuous distribution first the modal class is determined. The class interval
corresponding to the highest frequency is called modal class.
• 1. Find mode for the following data. 64, 38,35,68,35,94,42,35,52,35
• 2. Calculate the mode for the following data.
• Size of Shoe: 5 6 7 8 9 10
• No.of Pairs: 38 43 48 56 25 22
• 3. Find the mode for the following data.
• Daily wages(in Rs): 20- 40 40- 60 60- 80 80- 100 100- 120 120- 140 140-160
• No . of employees: 21 28 35 40 24 18 10
MERITS AND DEMERITS OF MODE .
• Merits :
• 1. It is easy to understand and easy to calculate
• 2. It is unaffected by the presence of extreme values.
• 3. It can be obtained graphically from a histogram.
• 4. It can be calculated from frequency distribution with open-end classes.
• 5. It is not necessary to know all the items. Only the point of maximum concentration is
required.
• Demerits :
• (1) It is not rigidly defined .
• (2) It is not based on all observations.
• (3) It is affected by sampling fluctuations.
• (4) It is not suitable for further mathematical treatment .
UNIT 3. MEASURE OF DISPERSIONBY PROF. SWATI BHALERAO
FY BBA (Sem 2) – 205 – Business Statistics – Patten 2019
SYLLABUS
• 3.1 Concept and meaning of Measure of dispersion, Requirements of good Measure of
dispersion.
• 3.2 Types of Measure of Dispersion- Absolute & Relative Measure dispersion (Range, Standard
• Deviation (S.D.), Variance, Quartile Deviation, Coefficient of Range, Coefficient of Quartile
• Deviation, and Coefficient of Variation (C.V).
• 3.4. Combined Standard Deviation
• 3.5 Numerical Problems
WHY DO WE NEED TO STUDY THE MEASURE OF DISPERSION?
• The common averages or measures of central tendency indicate the general magnitude of the
data and give us a single value which represents the data, but they do not tell us the degree of
spread out or the extent of variability in individual items in a distribution. This can be known
by certain other measures called measures of dispersion.
• Dispersion in particular helps in finding out the variability of the data i.e., the extent of
dispersal or scatter of individual items in a given distribution. Such dispersal may be known
with reference to the central values or the common averages such as mean, median and mode
or a standard value; or with reference to other values in the distribution. The need for such a
measure arises because mean or even median and mode may be the same in two or more
distribution but the composition of individual items in the series may vary widely
RANGE
• Range is the simplest measure of dispersion.
• When the data are arranged in an array the difference between the largest and the
smallest values in the group is called the Range.
• Symbolically: Absolute Range = L - S, [where L is the largest value and S is the smallest
value]
• Relative Range = Absolute Range / sum of the two extremes
• Amongst all the methods of studying dispersion range is the simplest to calculate and to
understand but it is not used generally because of the following reasons
1. Since it is based on the smallest and the largest values of the distribution, it is unduly
influenced by two unusual values at either end. On this account, range is usually not
used to describe a sample having one or a few unusual values at one or the other end.
2. It is not affected by the values of various items comprised in the distribution. Thus, it
cannot give any information about the general characters of the distribution within the
two extreme observations.
• For example, let us consider the following three series:
• Series: A 6 46 46 46 46 46 46 46
• Series: B 6 6 6 6 46 46 46 46
• Series: C 6 10 15 25 30 32 40 46
• It can be noted that in all three series the range is the same, i.e. 40, however the
distributions are not alike: the averages in each case is also quite different. It is because
range is not sensitive to the values of individual items included in the distribution. It thus
cannot be depended upon to give any guidance for determining the dispersion of the
values within a distribution.
QUARTILE DEVIATION
• The dependence of the range on extreme items can be avoided by adopting this measure.
Quartiles together with the median are the points that divide the whole series of
observations into approximately four equal parts so that quartile measures give a rough
idea of the distribution on either side of the average.
• Since under most circumstances, the central half of the distribution tends to be fairly
typical, quartile range Q3 – Q1 affords a convenient measure of absolute variation. The
lowest quarter of the data (upto Q1) and the highest quarter (beyond Q3) are ignored.
The remainder, the middle half of the data above Q1 and below Q3 or (Q3 – Q1) are
considered
• This, when divided by 2, gives the semi-interquartile range or quartile deviation.
• In a symmetrical distribution, when Q3 (75%) plus Q1 (25%) is halved, the value reached
would give Median, i.e., the mid-point of 75% and 25%. Thus, with semi-interquartile range
50% of data is distributed around the median. It gives the expected range between which
50% of all data should lie. The Quartile Deviation is an absolute measure of dispersion .
The corresponding relative measure of dispersion is
STANDARD DEVIATION
• As we have seen range is unstable, quartile deviation excludes half the data arbitrarily and
mean deviation neglects algebraic signs of the deviations, a measure of dispersion that does
not suffer from any of these defects and is at the same time useful in statistic work is standard
deviation.
• In 1893 Karl Pearson first introduced the concept. It is considered as one of the best
measures of dispersion as it satisfies the requisites of a good measure of dispersion.
• The standard deviation measures the absolute dispersion or variability of a distribution.
• It is represented by σ (read as ‗sigma‘); σ 2 i.e., the square of the standard deviation is called
variance. Here, each deviation is squared.
• The mean of squared deviation, i.e., the square of standard deviation is known as variance.
Standard deviation is one of the most important measures of variation used in Statistics.
Let us see how to compute the measure in different situation.
UNIT 4. CORRELATION & REGRESSION BY PROF. SWATI BHALERAO
FY BBA (Sem 2) – 205 – Business Statistics – Patten 2019
SYLLABUS
• 4.1. Concept and meaning of Correlation, Types of correlation.
• 4.2. Methods to study Correlation:- Scatter Diagram, Karl Pearson correlation coefficient,
• Spearman Rank Correlation Coefficient ( with Repeated Ranks)
• 4.3 Numerical Problems on Correlation
• 4.4 Regression- Concept and meaning of regression, lines of regression equation of Y on X and X
• on Y.
• 4.5 Regression coefficients, properties of regression coefficients,
• 4.6 Numerical problems on Regression
INTRODUCTION
• Relationship between price and demand of a commodity When we collect the information
(data) on two of such characteristics it is called bivariate data. It is generally denoted by (X,Y)
where X and Y are the variables representing the values on the characteristics
• Following are some examples of bivariate data.
• a) Income and Expenditure of workers.
• b) Marks of students in the two subjects of Maths and Accounts.
• c) Height of Husband and Wife in a couple.
• d) Sales and profits of a company.
• Between these variables we can note that there exist some sort of interrelationship or
cause and effect relationship. i.e. change in the value of one variable brings out the change
in the value of other variable also.Such relationship is called as correlation.
• Therefore, correlation analysis gives the idea about the nature and extent of relationship
between two variables in the bivariate data
TYPES OF CORRELATION:
• There are two types of correlation.
• a) Positive correlation. and
• b) Negative correlation.
• Positive correlation: When the relationship between the variables X and Y is such that
increase or decrease in X brings out the increase or decrease in Y also, i.e. there is direct
relation between X and Y, the correlation is said to be positive. In particular when the
change in X equals to change in Y‘ the correlation is perfect and positive. e.g. Sales and
Profits have positive correlation.
• : Negative correlation When the relationship between the variables X and Y is such
that increase or decrease in X brings out the decrease or increase in Y, i.e. there is an
inverse relation between X and Y, the correlation is said to be negative. In particular when
the ‗change in X equals to change in Y‘ but in opposite direction the correlation is
perfect and negative. e.g. Price and Demand have negative correlation.
MEASUREMENT OF CORRELATION
• The extent of correlation can be measured by any of the following methods:
1. Scatter diagrams
2. Karl Pearson‘s co-efficient of correlation
3. Spearman‘s Rank correlation
SCATTER DIAGRAM:
• The Scatter diagram is a chart
prepared by plotting the values of X
and Y as the points (X,Y) on the
graph.
• Perfect Positive Correlation: If the
graph of the values of the variables is
a straight line with positive slope as
shown in Figure, we say there is a
perfect positive correlation between
X and Y. Here r = 1
• (ii) Imperfect Positive Correlation:
• If the graph of the values of X and Y
show a band of points from lower
left corner to upper right corner as
shown in Figure, we say that there is
an imperfect positive correlation.
Here 0 < r < 1.
• Perfect Negative Correlation: If the
graph of the values of the variables
is a straight line with negative slope
as shown in Figure, we say there is a
perfect negative correlation
between X and Y. Here r = –1.
• Imperfect Negative Correlation:
• If the graph of the values of X and Y
show a band of points from upper left
corner to the
• lower right corner as shown in Figure,
then
• we say that there is an imperfect
negative
• correlation. Here –1 < r < 0
• (v) Zero Correlation:
• If the graph of the values of X and Y do not show any of the above trend then we say that
there is a zero correlation between X and Y. The graph of such type can be a straight line
perpendicular to the axis, as shown in Figure 4.5 and 4.6, or may be completely scattered
as shown in Figure 4.7. Here r = 0.
KARL PEARSON’S CO-EFFICIENT OF CORRELATION.
• This co-efficient provides the
numerical measure of the
correlation between the variables X
and Y. It is suggested by Prof. Karl
Pearson and calculated by the
formula
• Remark : We can also calculate this
co-efficient by using the formula
given by
• The Pearson‘s Correlation co-
efficient is also called as the
‗product moment correlation co-
efficient‘ Properties of correlation
co-efficient ‗r‘ The value of ‗r‘ can
be positive (+) or negative(-) The
value of ‗r‘ always lies between –1
& +1, i.e. –1< r
REGRESSION ANALYSIS
• As the correlation analysis studies the nature and extent of interrelationship between the
two variables X and Y, regression analysis helps us to estimate or approximate the value
of one variable when we know the value of other variable
• Therefore we can define the ‗Regression‘ as the estimation (prediction) of one variable
from the other variable when they are correlated to each other. e.g. We can estimate the
Demand of the commodity if we know it‘s Price. Why are there two regressions? When
the variables X and Y are correlated there are two possibilities,
• (i) Variable X depends on variable y. in this case we can find the value of x if know the
value of y. This is called regression of x on .
• (ii) Variable depends on variable X. we can find the value of y if know the value of X. This
is called regression of y on x.
• Hence there are two regressions, (a) Regression of X on Y; (b) Regression of X on Y
FORMULAS ON REGRESSION EQUATION
UNIT 5. INDEX NUMBERSBY PROF. SWATI BHALERAO
FY BBA (Sem 2) – 205 – Business Statistics – Patten 2019
SYLLABUS
• 5.1 Concept and meaning of Index Number, Notations
• 5.2 Construction of Price Index Number, Problems in the construction of Index Number,
Cost of Living Index Number (CLI), Family Budget Index Number
• 5.3 Uses of Index Number
• 5.4. Numerical Problems.
INTRODUCTION
• Index number is an important statistical relative tool to measure the changes in a variable
or group of variables with respect to time, geographical conditions and other
characteristics of the variable(s).
• Index number is a relative measure, as it is independent of the units of the variable(s)
taken in to consideration. This is the advantage of index numbers over normal averages.
All the averages which we studied before are absolute measures, i.e. they are expressed
in units, while index numbers are percentage values which are independent of the units of
the variable(s). In calculating an index number, a base period is considered for comparison
and the changes in a variable are measured using various methods.
IMPORTANCE OF INDEX NUMBERS
• (1) It is a relative measure: As discussed earlier index numbers are independent of the
units of the variable(s), hence it a special kind of average which can be used to compare
different types of data expressed in different units at different points of time.
• (2) Economical Barometer: A barometer is an instrument which measures the
atmospheric pressure. As the index numbers measure all the ups and downs in the
economy they are hence called as the economic barometers.
• To forecast trends: Index numbers prove to be very useful in identifying trends in a
variable over a period of time and hence are used to forecast the future trends
• (3) To generalize the characteristics of a group: Many a time it is difficult to measure the
changes in a variable in complete sense. For example, it is not possible to directly measure the
changes in a business activity in a country. But instead if we measure the changes in the
factors affecting the business activity, we can generalize it to the complete activity. Similarly
the industrial production or the agricultural output cannot be measured directly.
• (5) To facilitate decision making: Future estimations are always used for long term and short
term planning and formulating a policy for the future by government and private organizations.
Price Index numbers provide the requisite for such policy decisions in economics.
PRICE INDEX NUMBERS
• The price index numbers are classified as shown in the following diagram:
• Notations:
• P0: Price in Base Year Q0: Quantity in Base Year
• P1: Price in Current Year Q1: Quantity in Current Year
• The suffix ‘0’ stands for the base year and the suffix ‘1’ stands for the
• current year.
COST OF LIVING INDEX NUMBER OR CONSUMER PRICE INDEX NUMBER
• There are two methods for constructing this index number:
• (1) Aggregative expenditure method and
• (2) Family Budget Method
• (1) In aggregative expenditure method we construct the index number by taking the base
year quantity as the weight. In fact this index number is nothing but the Laspeyre’s index
number.
• (2) In family budget method, value weights are computed for each item in the group and
the index number i
USE OF COST OF LIVING INDEX NUMBERS
• These index numbers reflect the effect of rise and fall in the economy or change in prices
over the standard of living of the people.
• 2. These index numbers help in determining the purchasing power of money which is the
reciprocal of the cost of living index number.
• 3. It is used in deflation. i.e. determining the actual income of an individual. Hence it also
used by the management of government or private organizations to formulate their
policies regarding the wages, allowance to their employees
