I am having A LOT of trouble trying to solve this problem...


New member
Jul 21, 2021
A quality control manager checks the precision of car engine parts produced in a plant. A car engine part needs to be 1.5 cm in diameter. However, during production these parts can sometimes come out to be more or less than 1.5 cm in diameter. If a sample of these parts has diameter far from 1.5 cm on average, then the sample is sent for reproduction.

On a production day, the following samples of car engine parts are found:

Sample A: 150 parts with sample mean diameter 1.495 cm and variance 0.36

Sample B: 150 parts with sample mean diameter 1.505 cm and standard deviation 0.9

Which sample of car engine parts is more likely to be sent for reproduction? Explain why.

I'm not quite sure how to solve this question, and I don't think my answer is correct. I thought that comparing the z-scores of a 1.5cm part for both samples would allow me to determine how common a 1.5cm hose is in each sample.

My z scores were as follows:

z = 0.00833333333333333 <-- Sample A
z= -0.005555555555555555 <-- Sample B

I thought that because Sample B's z score for a diameter of 1.5cm is closer to the average, then there would not be as many outliers and thus not as many car parts would be rejected.