1 statistical indicators and statistical thinking 1 dr. t s g peiris department of mathematics
TRANSCRIPT
1
Statistical Indicatorsand
Statistical Thinking
1
Dr. T S G Peiris
Department of Mathematics
2
• Why do we do statistics?
2
•What is statistics?
To understand and explain the “variability”
3
Why data
• As the global economy becomes increasingly electronic , the application of statistics to business and day to day applications has been increasing fast. 3
4
Why data are needed?
• Obtaining appropriate data is essential in conducting business/teaching/etc
• Data contain information needed to make a more informal decision in a particular situation.
4
5
The growth and development of statistics
• Widespread availability of software tools had led to an ever increasing application of statistical methods to business decision making.
• Today managers face problems/burdens, not having to make more and more decisions based on larger and larger volumes of data.
5
6
• Why we want to know about statistics?
Managers/Processionals have access to a large amount of
data.
Lack of knowledge of data and its variability by the managers is difficult to survive due to competition.That is to use available data to make decisions
6
7
• A market researcher needs to assess product characteristics to distinguish one product from another
• An investor wants to determine what firms are likely to have accelerated growth
• A lecturer wants to know the duration of which students access his notes in the website
7
8
• Dean of a Faculty wants to how students performed in an exam
• Students wants compare marks with others
• An engineer wants to know how traffic pass at a busy junction
Farmer wants to about prices of vegetables
8
9
In today’s world…• …we are constantly being bombarded with
statistics and statistical information. For example:– customer surveys – medical news – political polls – economic predictions– marketing information – scanner data
• How can we make sense out of all this data?• How do we differentiate valid from flawed
claims?
• What is statistics?9
10
• Statistics is a way to get information from data’
Data
Statistics
Information
Data: Facts,, collected together for reference or information.
Information: Knowledge communicated concerning some particular fact.
Statistics is a tool for creating new understanding from data. 10
11
Parameters
Population
Sample
Statistics
Subset
Key statistical concepts(Statistical Thinking)
11
12
Key statistical concepts (Statistical Thinking)
Population• A population is the group of all items of
interest to a statistics practitioner.• Frequently very large; sometimes infinite.
Sample• A sample is a set of data drawn from the
population.• Potentially very large, but less than the
population.. 12
13
Parameters
• A descriptive measure of a population.
Statistics• A descriptive measure of a
sample.
Key statistical concepts(Statistical Thinking)
13
14
Statistical inference (Decisions)• Statistical inference is the process of making an
estimate, prediction, or decision about a population based on a sample.
Parameter
Population Sample
Statistic
Inference
What can we infer about a population’s parameters based on a sample’s statistics? 14
15
Stats anxiety• A student is anxious about his statistics course, after he had
heard that the course is difficult. The lecturer provides last semester’s final exam marks to the student. What can be discerned from this list of numbers?
Data
Statistics
Information
List of last term’s marks.958970657857
New information derived about the statistics class.
e.g. Class average, proportion of class receiving F’s,most frequent mark,marks distribution, etc.
15
16
Thus statistic
• is a quantity that is calculated from a sample of data.
• It is used to give information about unknown values in the corresponding population.
16
17
Statistical Indicator
• Derived from the sample• A single or composite value to represent a
variability of the populationStudents performance indicatorsUniversity performance indicatorsEducational indicatorsEcological indicatorsHuman Resource IndicatorsSport indicatorsHealth indicatorsClimate indicatorBusiness indicators
18
Statistical Thinking
• As today's good decisions are driven by data. Professionals are increasingly required to justify decisions on the basis of data
• Statistical thinking is a science assisting you to make decisions under uncertainties
• To make thinking easier we use statistical indicators
19
Indicators to measure central tendency
2030405060708090
100
1 11 21 31 41 51 61 71 81 91
Index Number
Mea
n m
arks
20
Indicators to measure central tendency
• Mean = nxxn
i i/
1
Weighted mean =
n
1i i
n
1i ii
w w
xwx
In some cases, the data are weighted according to its importance
21
Variation in weighted mean
0.0
10.0
20.0
30.0
1 11 21 31 41 51 61 71 81 91
Index number
Wei
gh
ted
mea
n
22
Are both are the same?
What is the indicator to check the association?
Raw
Weig
ht
10090807060504030
90
80
70
60
50
40
30
Scatterplot of Weight vs Raw
23
Median=67 - as an indicator
A. means
Perc
ent
10090807060504030
100
80
60
40
20
0
Mean 67.99StDev 12.93N 100
Cumulative distribution of AMNormal
24
Selecting Mode as an indicator
MedianMean
25
Indicators to Measure dispersion
• (a) Sample variance:
)1()1(
)( 2222
n
xnx
n
xxs ii
(b) Range
)x(Min)x(Max ii
[37,93}
68, 12.9
26
Use of Standard Deviation (SD) as an indicator
20406080
100
1 11 21 31 41 51 61 71 81 91
Index number
Mar
ks
Mean Mean + SD Mean - SD
27
Quality of information and variation are inversely related
•The larger the variation in the data, the lower the quality of the data (i.e., information): the Devil is in the Deviations
28
• Other indicators to measure dispersion are Mean Absolute Deviation (MAD) and Coefficient of Variability (CV)
n
xxMAD
n
1i i
%100*xsd
CV
29
Why indicator CV is useful?
Eg. A manufacturer of television tubes has two types of tubes namely A and B. Mean life time tubes A and B are 1495 hrs and 1875 and SD of tubes are 220 hrs and 310 hrs respectively.
• The CV of A = 14.7%
• and CV of B = 16.5%
30
Indicators to Measure Percentiles
• First quartile (Q1): The sample 25th percentile (P25)
• Second quartile (Q2): The sample 50th percentile (P50) “median”
• Third quartile (Q3): The sample 75th percentile (P75)
• Inter quartile range (IQR): Q3 – Q1 • Desired Percentile:
100)1(
pnLp
31
Indicator to measure association between two variables
2i
2i
ii
XY)yy()xx(
)yy)(x(x
r
Correlation
Coefficient
32
Use of statistical indictors for decision making
• Use of Z – Score
3
)( 321 ZZZZ
i
iii S
XXZ
Consumer Price Index – CCPI
is an indicator to measure of the average change in
the prices paid by consumers for a specific basket of
goods and services over time in a country
10000
0101
qP
qPP
33
Z Score as a statistical indicator
Sub_1
Frequency
10080604020
20
15
10
5
0
Mean 64.92StDev 20.67N 100
Histogram of Sub_1Normal
Sub_2
Frequency
105907560453015
25
20
15
10
5
0
Mean 62.96StDev 18.23N 100
Histogram of Sub_2Normal
Distribution of raw marks
34
Z Score as a statistical indicator
Zsocre_1
Frequency
2.41.60.80.0-0.8-1.6-2.4
20
15
10
5
0
Mean 3.108624E-17StDev 1.000N 100
Histogram of Zsocre_1Normal
Zscore_2
Frequency
210-1-2-3
40
30
20
10
0
Mean -3.77476E-17StDev 1.000N 100
Histogram of Zscore_2Normal
Distribution of new indicator – Z score
35
Relationship between raw marks and Z score
Raw_mean
Zsc_
mean
1009080706050403020
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
Scatterplot of Zsc_mean vs Raw_mean
36
Consumer Price Index – CCPI
• It is a statistical indicator to measure of the average change in the prices paid by consumers for a specific basket of goods and services over time in a country.
Colombo Consumer Price Index (CCPI)
37
Weights used for Colombo Consumer Price Index (CCPI) – CCPI_N
Items Weight
Food and Beverages 46.71
Cloth and Footwear 3.08
Housing, Water, Electricity 18.29
Furnishing 3.22
Health 4.18
Transport 9.47
Communication 4.42
Recreation & Culture 2.18
Education 5.79
Miscellaneous 2.65
38
Grade Point Average _GPA
Credits
Credits sGradePoint GPA Overall
39
Use of statistical indictors for decision making
• Body Mass Index Body Mass Index (BMI) is an indicator
calculated from a person's weight and height.
BMI provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems .
HAS THIS UPDATED TO SL?
40
BMI - Indicator
• BMI indicates you are
Underweight for BMI less than 18.5,
Normal - 18.5 - 24.9
Overweight - 25.0 - 29.9
Obese > 30.0
41
BMI - Indicator
• high blood pressure (hypertension) • high LDL-cholesterol ("bad" cholesterol) • low HDL-cholesterol ("good" cholesterol) • high triglycerides • high blood glucose (sugar) • family history of premature heart disease • physical inactivity • cigarette smoking
42
Use of statistical indictors for decision making
• Human Development Index is an indicator to rank countries by level of "human
development", which usually also implies whether a country is a developed, developing or under developing
43
HDI - Indicator
• Go to Websites
44
Thank you
and
Best Wishes