Aresearcher compares the effectiveness of two different instructional methods for

99% confidence interval = [-35.47,-26.53]

Step-by-step explanation:

For Method 1:

For Method 2:

We need to find the 99% confidence interval for the true difference between testing averages for students using Method 1 and students using Method 2.

Step 1: Find the point estimate for the true difference between the population means.

Therefore the point estimate for the true difference between the population means is -31.

Step 2: Find margin of error at 99% confidence.

From the standard normal table the critical value of z at 99% confidence = 2.576.

The formula for margin of error:

Substitute the values.

Therefore, the margin of error is 4.47.

Step 3: Find 99% confidence interval.

Therefore, the 99% confidence interval is [-35.47,-26.53].

7 or more hours

15 + 15 is 30