Historically,the average time to service a customer complaint has been 3 days and the standard deviation has been 0.50 day.Management would like to specify the control limits for an chart with a sample size of 10- and 3- sigma limits.Suppose the next sample of 10 yielded the following result: 3.2,2.1,3.6,2.8,3.9,3.5,2.7,4.1,2.6,and 3.3.What conclusion can be drawn?
A)Assuming the process variability is in control,the process average is also in statistical control.
B)Assuming the process average is in control,the process average is out of statistical control.
C)The sample size should be increased.
D)No conclusion can be drawn because there is insufficient data.

Question

Historically,the average time to service a customer complaint has been 3 days and the standard deviation has been 0.50 day.Management would like to specify the control limits for an  chart with a sample size of 10- and 3- sigma limits.Suppose the next sample of 10 yielded the following result: 3.2,2.1,3.6,2.8,3.9,3.5,2.7,4.1,2.6,and 3.3.What conclusion can be drawn?
A)Assuming the process variability is in control,the process average is also in statistical control. 
B)Assuming the process average is in control,the process average is out of statistical control. 
C)The sample size should be increased. 
D)No conclusion can be drawn because there is insufficient data.

Quizplus · Accepted Answer

The sample mean is 3.11, which is within the control limits of 2.29 and 3.71 (calculated using the formula: mean +/- 3*(standard deviation/square root of sample size)) at the 3-sigma level. Additionally, the sample mean is not unusually high or low compared to historical data. Therefore, assuming that the process variability is in control, we can conclude that the process average is in statistical control.

Historically,the Average Time to Service a Customer Complaint Has Been