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In statistics, a frequency distribution is a list of the
values that a variable takes in a sample. It is
usually a list, ordered by quantity, showing the number of times each value appears. For example, if 100 people rate a five-point
attitude item assessing their
agreement with a statement on a scale on which 1 denotes strong agreement and 5 strong disagreement, the frequency distribution
of their responses might look like:
| Rating |
Degree of agreement |
Number |
| 1 |
Strongly agree |
25 |
| 2 |
Agree somewhat |
35 |
| 3 |
Not sure |
20 |
| 4 |
Disagree somewhat |
15 |
| 5 |
Strongly disagree |
5 |
Statistical hypothesis testing is
founded on the assessment of differences and similarities between frequency distributions. This assessment involves measures of
central tendency or averages, such as the mean and median, and measures of variability or statistical dispersion, such as the standard deviation or variance.
A frequency distribution is said to be skewed when its mean and median are
different. The kurtosis of a frequency distribution is the concentration of scores
at the mean, or how peaked the distribution appears if depicted graphically—for example, in a histogram. If the distribution is more peaked than the normal distribution it is said to be leptokurtic; if less peaked it is said to be platykurtic.
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