EXAMPLE 1.30

Suspected outliers for call length data. For the call length data in Table 1.2 (page 17),

1.5 × IQR = 1.5 × 145.5 = 218.25

Any values below 54.5 − 218.25 = −163.75 or above 200 + 218.25 = 418.25 are flagged as possible outliers. There are no low outliers, but the eight longest calls are flagged as possible high outliers. Their lengths are

438 465 479 700 700 951 1148 2631

It is difficult to imagine calls lasting this long.