Unformatted text preview: age start with graphs. Then add numerical summaries. Distributions
v༇ Distribution of a variable
What possible values the variable takes and how frequently
it takes those values. There are many methods to describe and display distributions. Distributions of Categorical Variables
The values of a categorical variable are the labels for the categories. The
distribution of a categorical variable is described by either the count or the
percent of individuals who fall in each category.
Example: BUAD310: Class Composition [2 sections taken together]
CLASS LEVEL
U1
U2
U3
U4 Count
43
57
33
13 Percent
29.452
39.041
22.603
8.904 Graphs for Categorical Variables
v༇ In the bar chart the height of each bar is proportional to the
count (or percent) in each category Graphs for Categorical Variables
v༇ In the pie chart the area of each piece is proportional to the
percent of individuals in each category Bar charts and Pie charts
• Bar chart is called a Pareto chart when the
categories are sorted by frequency (popular in quality
control). • Pie charts are commonly chosen to illustrate market
shares or sources of revenue for a company. • Pie charts are less useful than bar charts if we want to
compare actual counts (easier to compare bars than
angles of wedges). Bar charts and Pie charts
BUAD310: Student Composition Bar charts and Pie charts BUAD310: Student Composition Correct Charts & the Area Principle • The area occupied by a part of the graph/chart that displays data should be proportional to the amount of data it represents. • Charts decorated to attract attention often violate the area principl...
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 Fall '07
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