(i) A random sample of 20 students is taken from a population. Each member of the random sample is asked to perform a simple task and the time taken to complete the task is recorded in each case (in minutes). The times are as follows: 16 20 21 21 20 21 22 21 22 17 16 23 21 24 21 16 25 20 17 23 (a) Obtain a stem-and-leaf diagram for the data set. (b) Find the mean, the standard deviation and the upper and lower quartiles. (c) Draw a modified box plot representative of the data set