Two hundred students are enrolled in an Economics class. After the first examination, a random sample of 6 papers was selected. The grades were 65, 75, 89, 71, 70 and 80.
a. Determine 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 95% confidence interval for the mean grade of all the students in the class.