2. A statistics professor is used to having a variance in his class grades of no more than 100. He feels that his current group of students is different, and so he examines a random sample of midterm grades (listed below.) At a = 0.05, can it be concluded that the variance in grades exceeds 100?

Question

2.	A statistics professor is used to having a variance in his class grades of no more than 100. He feels that his current group of students is different, and so he examines a random sample of midterm grades (listed below.) At a = 0.05, can it be concluded that the variance in grades exceeds 100? 
92.3	 	89.4 		96.7 		69.5 		88.5 		79.2 
76.9 		65.2		 49.1 		72.8 		67.5		 52.8 
72.9		 68.7 		75.8

PsyDAG · Answer

To calculate variance of ungrouped data;

Find the mean of the (μ) numbers given.
Subtract the mean from each of the numbers (x), square the difference and find their sum.
Divide the result by the total number of observations (N).