Reports and Visualizations

Gravetter & Wallnau, Chapter 2; Young, Chapter 2

Copyright 1997-8 by Forrest W. Young.

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Frequency Distribution Tables (Reports)

Frequency Distributions
A frequency distribution is an organized tabulation of the number of individuals located in each category of a variable's scale of measurement (potential scores).

Frequency Distribution Tables (Reports)
A table which presents the variable's scale of measurement (potential scores) by listing the different measurement categories (X values) in a column from highest to lowest.

Beside each X value is indicated the frequency (number of time the potential score occurs in the data). Usually the variable name is used as the heading of the scores column (or the letter X), and an "f" is the heading of the frequency column.

Note that the X values in the table represent the scale of measurement, not the actual scores. For example, in the table to the right the number 10 appears only once, even though the score was obtained twice. Also, the number 5 appears even though it wasn't an observed score.

  • The total number of observations can be obtained by summing up all the individual frequencies. The formula is
  • The total sum of scores is not obtained by summing up the values listed in the X column. This ignores the frequency of each score. Thus, we must multiply each score in the X column by its frequency to get the total sum of scores. The formula is:

Proportions & Percentages
Proportions and percentages are additional measures that describe the distribution of scores, and that are often incorporated into a basic frequency distribution table.

  • Proportions measure the fraction of the total group of scores that is associated with each score. Proportions are sometimes called relative frequencies, since they express frequency relative to total number. The formula for a proportion is:
  • Percentages are simply 100 times the proportion: