Confidence Intervals

Question

Twenty-five seniors from a large metropolitan area school district volunteer to allow their math SAT test scores to be used in a study. These 25 seniors had a mean math SAT score of = 450. Suppose we know that the standard deviation of the population of math SAT scores for seniors in the district is  = 100. Assuming the population of math SAT scores for seniors in the district is approximately normally distributed, compute a 90% confidence interval for the mean math SAT score  for the population of seniors.

Answer 1

the error margin is 1.65* 100 / sqrt(25) = 1.65*100 / 5 = 165./5 = 33

the confidence interval is (450-33, 450+33) = (417,483)

We are 90% confident the population mean is between 417 and 483