Lifetime of electronics: In a simple random sample of 100 electronic components produced by a certain method, the mean lifetime was 125 hours. Assume that component lifetimes are normally distributed with population standard deviation = 20 hours. Round the critical value to no less than three decimal places.

Find the sample size needed so that a 99.5% confidence interval will have a margin of error of 3. A sample size of is needed so that a 99.5% confidence interval will have a margin of error of 3. Round the sample size up to the nearest integer.