The times it took a random sample of runners to Time taken complete a race are summarised in the table. (t minutes) Frequency a Work out the lower quartile. 20-29 5 b Work out the upper quartile.) 30-39 10 c Work out the interquartile range. The mid-point of each class was represented by x and its corresponding frequency by giving: 40-49 36 50-59 20 fx-3740 Efx-183040 60-69 9 d Estimate the variance and standard deviation for these data.

AppendixLO1