In a random sample of 1,000 exams, the average score was 500 points with a standard deviation of 80 points.

find the interval about the sample mean such that the probability is 0.90 that the mean number lies within the interval.

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?

Keith runs 5 miles in 38 minutes. at the same rate, how many miles would he run in 57 minutes

Brad earns $12.75/hr and works 40 hours a week. what is his gross annual income?