A random sample of 49 cast aluminum pots is taken from a production line once every day.The number of defective pots is counted.The proportion of defective pots has been closely examined in the past and is believed to be 0.05. Refer to Exhibit 7-11.The sample proportions for the week are shown in the accompanying table. Is the production process in control?
A)No,since the sample proportions show a downward trend
B)No,since the sample proportions fall within the upper and lower control limits
C)Yes,since the sample proportions show a downward trend
D)Yes,since the sample proportions fall within the upper and lower control limits

Question

A random sample of 49 cast aluminum pots is taken from a production line once every day.The number of defective pots is counted.The proportion of defective pots has been closely examined in the past and is believed to be 0.05. Refer to Exhibit 7-11.The sample proportions for the week are shown in the accompanying table.  Is the production process in control?
A)No,since the sample proportions show a downward trend 
B)No,since the sample proportions fall within the upper and lower control limits 
C)Yes,since the sample proportions show a downward trend 
D)Yes,since the sample proportions fall within the upper and lower control limits

Quizplus · Accepted Answer

The sample proportions fall within the upper and lower control limits, which indicates that the production process is in control. The fact that there may be a downward trend in the sample proportions does not necessarily mean that the process is out of control.

A Random Sample of 49 Cast Aluminum Pots Is Taken