(Two-Sample t-Test Assuming Equal Variances) The test scores on the same algebra test were recorded for eight students randomly selected from students taught by teacher A and nine students randomly selected from students taught by Teacher B. Is there a difference in the average scores for students taught by these two teachers?

1. The data can be entered into the worksheet in one of three ways:
• Enter measurements from both samples into a single column and enter letters (A or B) in a second column to identify the sample from which the measurement comes.
• Enter the samples in two separate columns.
• If you do not have the raw data, but rather have summary statistics, MINITAB will allow you to use these values by selecting “Summarized data” in the top drop-down list and entering the appropriate values in the boxes.
2. Use the second method and enter the data into two columns of the worksheet. Use Stat ➤
Basic Statistics ➤ Display Descriptive Statistics to find the standard deviations for the two samples, s 59.91 1 and s 58.80 2 . Since the ratio of the two variances is s /s 51.27 1 2 2 2 (less than 3), you are safe in assuming that the population variances are the same.
3. Select Stat ➤ Basic Statistics ➤ 2-Sample t to generate the Dialog box in Figure 10.25(a).
Select “Each sample in its own column” from the drop-down list at the top of the dialog box, and select the appropriate columns from the list at the left. Click Options, check the “Assume equal variances” box and select the proper alternative. The two-sample output when you click OK twice automatically contains a 95% one- or two-sided confidence interval as well as the test statistic and p-value (you can change the confidence coefficient if you wish). The output is shown in Figure 10.25(b).

Transcribed Image Text:

Teacher A 65 88 Teacher B 91 85 93 93 70 70 95 62 82 80 60 92 22 76 76 898 10 79 77 98 86 87 75 15