Q7 Efficient manufacturing Efficiency experts study the proc

Q7

Efficient manufacturing: Efficiency experts study the processes used to manufacture items in order to make them as efficient as possible. One of the steps used to manufacture a metal clamp involves the drilling of three holes. In a sample of 55 clamps, the mean time to complete this step w-as -10.7 seconds. Assume that the population standard deviation is sigma = 12 seconds. Part 1 Construct an 80% confidence interval for the mean time needed to complete this step. Round to one decimal place, if necessary. An 80% confidence interval for the mean is . Part 2 out of 2 Find the sample size needed so that a 95% confidence interval will have margin error of A sample size of is needed in order to obtain a 95% confidence interval with a margin error of 1.5.

Solution

n = (z*sd/E)^2

the z score to use for a 95% confidence interval is 1.96

n = (1.96*12/1.5)^2

n = 246, always round up

answer: 246