1.5 Measures of Spread (Median)

Range = max value – min value

Quartiles a quartile represents 25% of the data. The median is the middle quartile.

Interquartile Range (IQR) = upper quartile – lower quartile, or in short,

Displaying Spread Graphically

Box and Whisker Plot

A box and whisker plot does not include outliers. The textbook has a ‘test’ for outliers which you can use. This test is not a hard-and-fast rule and should be used with consideration for the context.

Upper boundary = upper quartile + 1.5 IQR

Lower boundary = lower quartile - 1.5 IQR

Any data outside of these boundaries can be considered outliers.

p. 143# 1-6

p. 148# 1-4