Transforming Data

Measures of Center

Measures of Center change when data is added, subtracted, multiplied, or divided.

Measures of Spread

Measures of spread change only when data is multiplied or divided.

Example:

mean: 17 median: 18 IQR: 5 SD: 3.4      range: 13

add 2 to each data point

mean: 19 median: 20 IQR: 5 SD: 3.4   range: 13

multiply each data point by 3

mean: 57 median: 60 IQR: 15 SD: 10.2  range: 39

x/5 - 3

mean: 8.4 median: 9 IQR: 3 SD: 2.04   range: 7.8