Measures of variability:
o Standard Deviation
Parametric average: arithmetic computations involved, for example Mean. (Not usually for
mode and median).
Range: upper real limit of highest score minus the lower real limit of lowest score.
o Outliers (ie: extreme scores) change the range.
Median is also known as 5 percentile. If you divide range into 4 parts, 1 quarter (1 ) is 25
percentile, last quarter (Q ) is 100 percentile.
Formula for ‘SS’ (in lecture slides): is sum of squared deviations from the mean.