Q 88

Fifty students are enrolled in an Economics class. After the first examination, a random sample of 5 papers was selected. The grades were 60, 75, 80, 70, and 90.
a.Calculate the estimate of the standard error of the mean.
b.What assumption must be made before we can determine an interval for the mean grade of all the students in the class? Explain why.
c.Assume the assumption of Part b is met. Provide a 90% confidence interval for the mean grade of all the students in the class.
d.If there were 200 students in the class, what would be the 90% confidence interval for the mean grade of all the students in the class?

Q 89

A local university administers a comprehensive examination to the recipients of a B.S. degree in Business Administration. A sample of 5 examinations is selected at random and scored. The scores are shown below.
Use Excel to determine an interval estimate for the mean of the population at a 98% confidence level. Interpret your results.