NJCU has launched Interfolio platform, a new online platform through which all employees can apply tenure, promotions and other professional developmental applications. University conducted multiple training sessions so that all the employees can use the system smoothly and efficiently. Because of the attendance in the training session was not mandatory, some employees didn't attend. Two groups of nine employees for each group were considered where one group attended the training session and the other group didn't. The time (in minutes) for completing the application process for each group are given in the following table.

Not attended 31 38 33 28 45 44 35 31 34

Attended 34 32 22 34 40 26 29 30 26

Estimate the population mean difference (1 2) with confidence interval 95%. Assume that population variances of two groups are equal and completing times are approximately normally distributed.