

Minitab v13 
Hypothesis Testing: Continuous Variables (2 Sample)
The Minitab Project is available. It contains the following data:
Type t Data Format Column N Comments Between
or Indep
endent
Groupsunstacked Written 9 scores on the written papers Typed 10 scores on the written papers stacked Code 19 dummy codes for groups
(1=written, 2=typed)Scores 19 all of the "Written" & "Typed" data Paired or
Dependent GroupsRed 10 reaction times to red lights Greed 10 reaction times to green lights
t test  Between Groups
Use the "2Sample t..." command off of the "Stat, Basic Statistics" menu. That is:
That will take you to the following dialog box:
For the first part of this example choose "Samples in different columns" and type the relevant variable(s) in the box (or double click them from the left hand menu). Make sure the "Assume equal variances" box is checked. You might check the "Options..." button to verify that alpha is set to .05 with a nondirectional test. Since we are dealing with only two means, we won't bother with a graph. The output will look like this:
TwoSample TTest and CI: Written, Typed
Twosample T for Written vs TypedN Mean StDev SE Mean
Written 9 82.00 4.03 1.3
Typed 10 85.60 3.03 0.96Difference = mu Written  mu Typed
Estimate for difference: 3.60
95% CI for difference: (7.03, 0.17)
TTest of difference = 0 (vs not =):
TValue = 2.22 PValue = 0.041 DF = 17
Both use Pooled StDev = 3.53We could have also run this test with stacked data (where each subject would represent a row in the worksheet) rather than unstacked where the two groups are in separate columns. Stacked data is actually a more realistic approach, since we typically record multiple DV's as well as demographic and other information for each subject. Having each subject represent one row of data is convenient and efficient.
For stacked data we would chose "Samples in one column" in the dialog box and typed the dependent variable in the "Samples:" box and the codes with the levels of the IV in the "Subscripts:" box.
Again it is important to make sure the "Assume equal variances" box is checked. In this case, the output would look like this:
TwoSample TTest and CI: Scores, Code
Twosample T for Written2 vs TypedCode N Mean StDev SE Mean
1 9 82.00 4.03 1.3
2 10 85.60 3.03 0.96Difference = mu (1)  mu (2)
Estimate for difference: 3.60
95% CI for difference: (7.03, 0.17)
TTest of difference = 0 (vs not =):
TValue = 2.22 PValue = 0.041 DF = 17
Both use Pooled StDev = 3.53
t test  Dependent Groups
Use the "Paired t..." command off of the "Stat, Basic Statistics" menu. That is:
That will take you to the following dialog box:
Type the relevant variable(s) for the "First sample:" and "Second sample:" as Minitab calls these multiple measurements (or double click them from the left hand menu). You might check the "Options..." button to verify that alpha set to .05 with a nondirectional test. Since we are dealing with only two means, we won't bother with a graph. The output will look like this:
Paired TTest and CI: Red, Green Paired T for Red  Green
N Mean StDev SE Mean
Red 10 25.30 5.66 1.79
Green 10 27.90 4.75 1.50
Difference 10 2.60 3.27 1.0395% CI for mean difference: (4.94, 0.26)
TTest of mean difference = 0 (vs not = 0):
TValue = 2.51 PValue = 0.033