Question

1. A certain change in a manufacturing process is being considered. Samples are taken from both the existing and the new process to determine if the change will result in an improvement. If 110 of 1440 items from the existing process are found defective, and 78 of 1785 items from the new process are found defective. At 90% confidence level what would you conclude?

2. Estimate the variance of filling a cannery, for 10 cans were selected at random and their contents are weighed and the standard deviation is 0.01. Construct a 90% confidence interval for estimating the variance σ2.

3. A random sample of n1=15 measurements on the breaking strength of a certain type of material has ?2=3.21 (psi)2. Repeated measurements on a second machine with n2=9 shows ?2=2.32 (psi)2. Assuming that the measurements are normally distributed, would you conclude that the two variances are significantly different at the 90% confidence level?

Answer 1