FREQUENCY DISTRIBUTIONS raw score distribution: list of each individual’s score frequency distribution: list of each score that appears and how many times each score occurs

Uses of Frequency Distributions Summarize a large set of data. Describe the shape of a distribution. Needed for inferential statistics.

A Raw Score Distribution

Frequency Distribution Table xf

Frequency Polygon Best for quantitative/continuous data. Study Time in Hours f

Histogram Best for quantitative/continuous data. Study Time in Hours f

Bar Graph Best for qualitative/discrete variables. f Ed. Bus. A&S AST College

Guidelines for Graphs Label units. Make axes proportional (y axis should be 2/3 to 3/4 length of x axis). Make bars equal width. Keep it simple.

Describing Frequency Distributions symmetrical: same on both sides

skewed: scores piled on one side positive skew negative skew body tail

kurtosis: steepness leptokurtic platykurtic mesokurtic

Frequency Distribution Statistics relative frequency: proportion of scores that are x cumulative frequency: number of scores up to and including x percentile rank: percentage of scores up to and including x percentile: x score at a percentile rank

Cumulative Frequency xfcf start at the bottom score add the frequencies always equals N, total # of scores

Relative Frequency xfrf divide each frequency by N 5/50 =.10 3/50 =.06 8/50 =.16 9/50 =.18 10/50 =.20 7/50 =.14

Percentile Rank xfcfpr divide cf by N and multiply by th %ile = 7 90th %ile = 6 84th %ile = 5 68th %ile = 4 52nd %ile = 3 34th %ile = 2 14th %ile = 1