09 patterns in data
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14-04-2012
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Research Methodology Dr. Nimit Chowdhary, Professor
Saturday, April 14, 2012 1© Dr. Nimit Chowdhary
How to describe patterns in quantitative data?1. Center2. Spread3. Shape4. Unusual features
Saturday, April 14, 2012 © Dr. Nimit Chowdhary Research Methodology Workshop p. 2
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A histogram is made up of columns plotted on the graph
Frequency
Quantitative variable
Chap 2-4
Presents data in a way that provides substance, statistics and design
Communicates complex ideas with clarity, precision and efficiency
Gives the largest number of ideas in the most efficient manner
Almost always involves several dimensions Tells the truth about the data
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Smith/Davis (c) 2005 Prentice Hall
There are several types of graphs from which the researcher can choose. Your choice of graphs will be determined by which one depicts your results most effectively and by the scale of measurement you used.
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Smith/Davis (c) 2005 Prentice Hall
Pie Chart – depicts the percentage represented by each alternative as a slice of a circular pie; the larger the slice, the greater the percentage.
Smith/Davis (c) 2005 Prentice Hall
Presents data in terms of frequencies per category. A bar diagram is constructed when one is using nominal (or qualitative) categories that cannot be numerically ordered from lowest to highest.
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Smith/Davis (c) 2005 Prentice Hall
Histogram –represents quantitative data in terms of frequencies.
Like the histogram, polygon displays the frequency of each number or score. The only differences between these two graphs are the use of bars in the histogram and the use of connected dots in the frequency polygon.
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In line graphs, there are two axes or dimensions that must be discussed.
One of the variables is plotted on the ordinate and the other is plotted on the abscissa.
How tall should the Y axis be? How long should the X axis be? A good rule of thumb is
for the Y axis to be approximately two thirds as tall as the X axis is long.
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Day Chocolate Strawberry WhiteMonday 53 78 126Tuesday 72 97 87Wednesday 112 73 86Thursday 33 78 143Friday 76 47 162
The cafeteria wanted to collect data on how much milk was sold in 1 week. The table below shows the results. We are going to take this data and display it in 3 different types of graphs.
A bar graph is used to show relationships between groups.
The two items being compared do not need to affect each other.
It's a fast way to show big differences. Notice how easy it is to read a bar graph.
Chocolate Milk Sold
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A circle graph is used to show how a part of something relates to the whole.
This kind of graph is needed to show percentages effectively.
Chocolate Milk Sold
MondayTuesdayWednesdayThursdayFriday
A line graph is used to show continuing data; how one thing is affected by another.
It's clear to see how things are going by the rises and falls a line graph shows.
Chocolate MIlk Sold
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Chocolate MIlk Sold
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Chocolate Milk Sold
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Bar Graph
Line Graph
Circle (Pie) Graph
The same data displayed in 3 different types of graphs.
Chocolate Milk Sold
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Chap 2-18
Using “chart junk” Failing to provide a relative
basis in comparing data between groups
Compressing the vertical axis Providing no zero point on
the vertical axis
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Chap 2-19
Good Presentation
1960: $1.00
1970: $1.60
1980: $3.10
1990: $3.80
Minimum Wage Minimum Wage
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1960 1970 1980 1990
$
Bad Presentation
Good PresentationA’s received by
students.A’s received by
students.
Bad Presentation
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FR SO JR SR
Freq.
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FR SO JR SR
%
FR = Freshmen, SO = Sophomore, JR = Junior, SR = Senior
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Chap 2-21
Good PresentationQuarterly Sales Quarterly Sales
Bad Presentation
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Q1 Q2 Q3 Q4
$
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Q1 Q2 Q3 Q4
$
Chap 2-22
Good PresentationMonthly Sales
Monthly SalesBad Presentation
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J F M A M J
$
36394245
J F M A M J
$
Graphing the first six months of sales.
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