A researcher compares the effectiveness of two different instructional methods for teaching pharmacology. A sample of 49 students using Method 1 produces a testing average of 72.8. A sample of 31 students using Method 2 produces a testing average of 72.3. Assume that the population standard deviation for Method 1 is 6.29, while the population standard deviation for Method 2 is 15.7. Determine the 90% confidence interval for the true difference between testing averages for students using Method 1 and students using Method 2.