If you have been given or calculated the sample mean and sample standard deviation together with the sample size for the differences between two treatments you can use the Statlets window presented below.

ACTIVITY

Eight pairs of slow learners with similar reading IQs are found, one member of each pair is randomly assigned to the standard teaching method while the other is assigned to the new method. The difference (New Method - Standard Method) in reading test scores for the eight subjects has a mean of 4.375, and a standard deviation of 1.685.

a. Form a 95% confidence interval for the mean difference (New Method - Standard Method) in reading test scores.

• Step 1: Make sure that "Input" menu option is selected.
• Step 2: Type "Difference" in the "Data label" box.
• Step 3: Type "8" in the "Sample size" box.
• Step 4: Type "4.375" in the "Sample mean" box.
• Step 5: Type "1.685" in the "Sample standard deviation" box.
• Step 6: Select the "t test" from menu options.

The output will include: Sample size, Mean difference, and Standard deviation of the difference followed by 95% confidence interval for the population mean difference.

b. Find a 99% confidence interval by following the steps given below:

• Step 1: Make sure that "Input" menu option is selected.
• Step 2: Type "Difference" in the "Data label" box.
• Step 3: Type "8" in the "Sample size" box.
• Step 4: Type "4.375" in the "Sample mean" box.
• Step 5: Type "1.685" in the "Sample standard deviation" box.
• Step 6: Select the "t test" from menu options.
• Step 7: Click on the "Options" button on the upper right hand side of the window.
• Step 8: Change only Alpha from 5.0 to 1.0.
• Step 9: Click on the "OK" button.

The output will include: Sample size, Mean difference, and Standard deviation of the difference followed by 99% confidence interval for the population mean difference.

c. By using your answers to a and b, what can you say about the effectiveness of the new method?