A random sample of 25 statistics examinations was selected….

A random sample of 25 statistics examinations was selected. The average score in the sample was 76 with a standard deviation of 12. Assuming the scores are normally distributed, the 99% confidence interval for the population average examination score is _____.

A machine that produces a major part for an airplane engine…

A machine that produces a major part for an airplane engine is monitored closely. In the past, 10% of the parts produced would be defective. With a 0.95 probability, the sample size that needs to be taken if the desired margin of error is 0.04 or less is

Let’s assume that we do not have population standard deviati…

Let’s assume that we do not have population standard deviation from data of previous studies, but have information on range: the smallest value of the sample is 4 and the largest value of the sample is 40. Then, at 90% confidence, how large a sample would provide a margin of error of 2.