bar graph
A graph in which a free-standing vertical bar is centered over each score on the X axis; used with nominal or ordinal scores.
bimodal distribution
A symmetrical frequency polygon with two distinct humps where there are relatively high-frequency scores and with center scores that have the same frequency.
cumulative frequency
The frequency of the scores at or below a particular score; symbolized by cf.
distribution
An organized set of data.
frequency
The number of times each score occurs within a set of data; also called simple frequency; symbolized by f.
frequency polygon
A graph that shows interval or ratio scores (X axis) and their frequencies (Y axis), using data points connected by straight lines.
grouped distribution
A distribution formed by combining different scores to make small groups whose total frequencies, relative frequencies, or cumulative frequencies can then be manageably reported.
histogram
A graph similar to a bar graph but with adjacent bars touching, used to plot the frequency distribution of a small range of interval or ratio scores.
negatively skewed distribution
A frequency polygon with low-frequency, extreme low scores but without corresponding low-frequency, extreme high ones, so that its only pronounced tail is in the direction of the lower scores.
normal curve
The symmetric, bell-shaped curve produced by graphing a normal distribution.
normal distribution
A set of scores in which the middle score has the highest frequency, and proceeding toward higher or lower scores the frequencies at first decrease slightly but then decrease drastically, with the highest and lowest scores having very low frequency.
percentile
The percentage of all scores in the sample that are at or below a particular score.
positively skewed distribution
A frequency polygon with low-frequency, extreme high scores but without corresponding low-frequency, extreme low ones, so that its only pronounced tail is in the direction of the higher scores.
proportion of the area under the curve
The proportion of the total area beneath the normal curve at certain scores, which represents the relative frequency of those scores.
rectangular distribution
A symmetric frequency polygon shaped like a rectangle; it has no discernible tails because its extreme scores do not have relatively low frequencies.
relative frequency
The proportion of time a score occurs in a distribution, equal to the proportion of the total number of scores that is made up by the score’s simple frequency; symbolized by rel. f.
relative frequency distribution
A distribution of scores, organized to show the proportion of time each score occurs in a set of data.
simple frequency
The number of times that a score occurs in data.
simple frequency distribution
A distribution of scores, organized to show the number of times each score occurs in a set of data.
tail (of a distribution)
The far-left or far-right portion of a frequency polygon, containing the relatively low-frequency, extreme scores.
ungrouped distribution
A distribution that shows information about each score individually.
