Chapter 2
Frequency Distributions
Chapter 2
Distributions
> Four different ways to visually describe just one variable
• Frequency table
• Grouped frequency table
• Frequency histograms
• Frequency polygon
Histogram for the Frequency Table of
Graduate Advisors
Histogram for the Grouped Frequency Table of TV Pacing
Index Data
Frequency Polygons as Another Graphing Option for the TV Pacing Index Data
Check Your Learning
> How old are the students in our class?
• Construct a frequency table; grouped frequency table; histogram; frequency polygon
> What is the best method of presentation for our data?
Shapes of Distributions
> Normal distributions: Specific frequency distribution
• Bell shaped
• Symmetrical
• Unimodal
The Normal Distribution
Skewed Distributions
> When our data are not symmetrical
• Positive: tail to the right
> May represent floor effects
• Negative: tail to the left
> May represent ceiling effects
• Memory hint: skew is where the tail is
Two Kinds of Skew
Everyone Improves
Helps the High Performers
Helps the Low Performers
