A simple random sample of size nequals23 is drawn from a population that is normally distributed. The sample mean is found to be x overbar equals 51 and the sample standard deviation is found to be sequals15. Construct a 95% confidence interval about the population mean.

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)