SCENARIO 8-2
A quality control engineer is interested in the mean length of sheet insulation being cut
automatically by machine.The desired mean length of the insulation is 12 feet.It is
known that the standard deviation in the cutting length is 0.15 feet.A sample of 70 cut
sheets yields a mean length of 12.14 feet.This sample will be used to obtain a 99%
confidence interval for the mean length cut by machine.
-True or False: Referring to Scenario 8-2, the confidence interval is valid only if the lengths
cut are normally distributed.

Question

Quizplus · Accepted Answer

The confidence interval is valid due to the Central Limit Theorem, which states that the sampling distribution of the sample mean will be approximately normal if the sample size is large enough (typically n > 30), regardless of the distribution of the population.

SCENARIO 8-2 A Quality Control Engineer Is Interested in the Mean Length