Answer:
The 98% confidence interval for the true difference between testing averages for students using Method 1 and students using Method 2 is (5.20, 7.60).
Explanation:
The (1 - α)% confidence interval for the difference between two population mean when the population standard deviations are known is:

The information provided is:

The critical value of z for 98% confidence interval is:

*Use a z-table for the critical value.
Compute the 98% confidence interval for the difference between two population means as follows:



Thus, the 98% confidence interval for the true difference between testing averages for students using Method 1 and students using Method 2 is (5.20, 7.60).