A test has a mean grade of 75 with standard deviation of 5. The distribution of test grades is normal. What percent of the test grades are below 60?
Joe wants to find a 90% confidence interval for his mean running time for his usual route. He has sample data for 30 days of running. The mean time for the 30 days is 22 minutes with standard deviation of 2 minutes. What is the 90% confidence interval of his overall mean running time?
What is the margin of error for a 98% confidence interval if we have a sample mean of 50, sample standard deviation of 6, and a sample size of 100?
Find the boundaries of the middle 70% of the data in a normal distribution that has a mean of 40 and standard deviation of 4.
What proportion of the prices of a pair of sneakers are above $150 if the mean price is $95 and the standard deviation is $15. Assume the prices are nor