n**Range
**

nhighest score minus the lowest score

nOutliers will skew your data

n**Interquartile Range** Ð 25th, 50th, 75th, 90th, etc
25th quartile Ð 25% of all scores fall below this
score

n 75th
quartile Ð 75% of all scores fall below this score

n**Semi-interquartile** Ð __Q3ÐQ1 __ (middle 50%) Ð not affected by outliers

2

nThese are **CRUDE
MEASURES OF VARIABILITY - **does not tell
the whole story about the raw data. A
mean of 5.3 does not tell if most of the scores
were similar. So, we have measures of variability, which **tell us ****about the
spread of the scores on the scale of measurement**.

n**Deviation
**

nthe distance from the mean

n+ is above mean, - is below the mean

n**Deviation scores** - MUST sum (S) to zero