To compare the effect of stress caused by noise on the ability to perform a simple task, 86 subjects were divided into two groups38 subjects as a control group, and 48 subjects as the experimental group. Although each subject performed the task, the experimental group had to perform the task while loud rock music was played. The time to finish the task was recorded for each subject and the following summary was obtained.

	Control	Experimental
n	38	48
x	17 minutes	24 minutes
s	5 minutes	11 minutes

(a)Find a 99% confidence interval for the difference in mean completion times (in minutes) for these two groups. (Calculate the difference as the control group the experimental group. Round your answers to two decimal places.) min to min(b)Based on the confidence interval in part (a), is there sufficient evidence to indicate a difference in the average time to completion for the two groups? Explain.The confidence interval in part (a) has ---Select--- two negative endpoints/ one positive and one negative endpoint/ two positive endpoints . Hence, it is ---Select--- plausible /not likely that the means are equal. Based on the data we would conclude that ---Select--- there is/ there is no evidence of a real difference in the mean times to completion for the two groups.