Given: n=130, σ = 25, level of confidence is 90%. What is the margin of error of the given data? Suppose that the amount of time spends by working students weekly is normally distributed with the...

Given: n=130, σ = 25, level of confidence is 90%. What is the margin of error of the given data?

Suppose that the amount of time spends by working students weekly is normally
distributed with the standard deviation of 25 minutes. A random sample of 125 observations is drawn and the sample mean is computed as 150 minutes.
Determine the 95% confidence interval estimate of the population mean.

Compute for the sample size needed if the margin of error is 85, with a sample standard deviation of 215 and a 99% level of confidence.