Determine the Appropriate Sample Size

The following work sampling data was collected from observing a retail assistant: 

Activity                                                           Number of observations

Attending to customers                                              60

Telephone enquiries                                                    150

Walking around                                                          40

Reading data                                                               30

Talking to manager                                                     40 

Talking to other workers                                             20 

Lunch/coffee/comfort breaks                                      50 

Dealing with customer complaints                              110 

                                                                                  Total 500

The figures mean that, say, over the course of a day, it is estimated that 22 per cent of the time was devoted to dealing with customer complaints. 

(a) Determine the limits of accuracy of the above calculation 

(b) If the accuracy needed was to be ±1 per cent, determine the appropriate sample size. 

(c) How would an operations manager use the data obtained from the exercise described?