Statistical procedures that are used to summarize sets of scores with respect to central tendencies, variability, and correlations.
Inferential statistics
Statistical procedures that allow researchers to determine whether the results they obtain support their hypotheses or can be attributed just to chance variation.
Frequency distribution
A summary of how frequently each score appears in a set of observations.
Measure of central tendency
A statistic, such as a mean, median, or mode, that provides one score as representative of a set of observations.
Mode
The score appearing most frequently in a set of observations; a measure of central tendency.
Median
The score in a distribution above and below which lie 50 percent of the other scores; a measure of central tendency.
Mean
The arithmetic average of a group of scores; the most commonly used measure of central tendency.
Measure of variability
A statistic, such as a range or standar deviation, that indicates how tightly the scores in a set of observations cluster together.
Range
The difference between the highest and lowest scores in a set of observations; the simplest measure of variability.
Standard deviation (SD)
The average difference of a set of scores from their mean; a measure of variability.
Correlational coefficient (r)
A statistic that indicates the degree of relationship between two variables.
Normal Curve
The symmetrical curve that represents the distribution of scores on many psychological attributes; allows researchers to make judgement of how unusual an observation or result is.