Glossary

Apparent limits	are the limits of a class interval in the same units as the original data.



Class intervals	are equal-sized groups of raw data used to summarize data in a grouped frequency distribution.



Cumulative frequency	( cum ƒ )is the total number of scores that fall below the upper real limit of an interval.



Cumulative percent	( cum %)is also known as percentile. It is the percentage of scores that fall below the exact upper limit of the interval. cum % = cum rel ƒ · 100



Cumulative relative frequency	( cum rel ƒ )is the total proportion of scores that lie below the real upper limit of the interval.



Frequency	( ƒ ) is the number of times a score occurs. The sum of the frequencies in a distribution is equal to the total number of scores in the distribution.



grouped frequency distribution	in this distribution, the raw data are combined into equal-sized groups called class intervals. The rule of thumb is to create between 10 and 20 class intervals and adjust the size of the intervals accordingly.



Midpoint	is the average (center) of a class interval.



Range	is the full extent of scores from the highest to the lowest in the distribution.



Ranked distribution	is a distribution of numbers in which scores are arranged in order (ranked), with the highest number at the top and the lowest number at the bottom of a list.



Raw data	are the scores or numbers that have been collected but not organized or summarized.



Real limits	are the true extensions of the lower apparent limit minus 0.5 unit and the upper apparent limit plus 0.5 unit.



Relative frequency	( rel ƒ )is the proportion of scores from the distribution that fall within the real limits of an interval.



Simple frequency distributions	are created by listing all possible score values in a distribution and then indicating the frequency.

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