| A | B |
|---|
| Variability | A measure of the degree to which the scores in a distribution are clustered together or spread apart. |
| Range | the total distance covered by the distribution |
| Interquartile Range | the distance covered by the middle 50% of the distribution |
| Standard Deviation | the standard distance between a score and the mean |
| first quartile | The score that separates the lowest 25% of a distribution from the highest 75%. |
| third quartile | The score that separates the lowest 75% of a distribution from the highest 25%. |
| deviation score | The distance (and direction) from the mean to a specific score. Deviation = X – μ. |
| population variance | The average squared distance from the mean; the mean of the squared deviations. |
| Formula for Population | SS = Σ(X – μ)2 |
| Formula for a sample | SS = Σ(X – M)2 |
