A housekeeping supervisor inspects rooms after the staff has cleaned them and compares their staff's performance against a checklist of items that should be cleaned, replaced, etc., according to standard operating procedure at the hotel. Over the past week she finds three rooms that have cleaning mistakes out of the 140 rooms she has inspected. How many additional rooms should she sample to establish an average fraction defective for the p chart she would like to make to monitor this process?
A)78
B)93
C)108
D)133

Question

Quizplus · Accepted Answer

In order to establish the average fraction defective for a p-chart, a sufficient sample size is needed. The minimum recommended sample size for a p-chart is 100, but if the process is not stable, a larger sample size may be necessary. In this case, with a total of 140 rooms inspected and only three rooms with cleaning mistakes, the fraction defective is very low. Assuming that the supervisor wants to create a p-chart with a 95% confidence level and a margin of error of 5%, the sample size needed would be approximately 93 rooms. Therefore, the best choice would be B) 93.

A Housekeeping Supervisor Inspects Rooms After the Staff Has Cleaned