Microsoft Office Tutorials and References
In Depth Information
5.1.2 STEP 2: Create a table that summarizes the sample size,
mean score, and standard deviation of each group
This step makes it easier for you to make sure that you are using the correct numbers
in the formulas for the two-group t-test. If you get the numbers “mixed-up,” your
entire formula work will be incorrect and you will botch the problem terribly.
For example, suppose that you tested college freshmen males on the perceived
effectiveness of “Ibuprofen” versus “Acetaminophen,” in which the males were
randomly assigned to use just one of these types of pain medication, and then to rate
its perceived effectiveness on a 100-point scale from 0
excellent.
After the research study was completed, suppose that the Ibuprofen group had 52
males in it, their mean effectiveness rating was 55 with a standard deviation of 7,
while the Acetaminophen group had 57 males in it and their average effectiveness
rating was 64 with a standard deviation of 13.
The formulas for analyzing these data to determine if there was a significant
different in the effectiveness rating for freshmen males for these two types of pain
medication require you to use six numbers correctly in the formulas: the sample
size, the mean, and the standard deviation of each of the two groups. All six of these
numbers must be used correctly in the formulas if you are to analyze the data
correctly.
If you create a table to summarize these data, a good example of the table, using
both Step 1 and Step 2, would be the data presented in Fig. 5.1 :
For example, if you decide to call Group 1 the Ibuprofen group and Group 2 the
Acetaminophen group, the following table would place the six numbers from your
research study into the proper calls of the table as in Fig. 5.2 :
You can now use the formulas for the two-group t-test with more confidence that
the six numbers will be placed in the proper place in the formulas.
Note that you could just as easily call Group 1 the Acetaminophen group and
Group 2 the Ibuprofen group; it makes no difference how you decide to name the
two groups; this decision is up to you.
¼
poor to 100
¼
Fig. 5.1 Basic Table Format for the Two-group t-test
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