Microsoft Office Tutorials and References
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F12:H13. Be sure to double-check your work or you will not be able to obtain the
correct answer to this problem if you have only one incorrect figure!
Since both groups have a sample size less than 30, you need to use Formula #2
for the t-test for the difference of the means of two independent samples.
Formula #2 for the two-group t-test is the following:
t ¼ X 1 X 2
S X 1 X 2
ð 5 : 1 Þ
s
n 1 1
ð
Þ S 1 þ n 2 1
ð
Þ S 2
1
n 1
þ 1
n 2
where S X 1 X 2 ¼
ð 5 : 5 Þ
n 1 þ n 2 2
and where degrees of freedom ¼ df ¼ n 1 þ n 2 2
ð 5 : 6 Þ
This formula is complicated, and so it will reduce your chance of making a
mistake in writing it if you ‘‘break it down into pieces’’ instead of trying to write
the formula as one cell entry.
Now, enter these words on your spreadsheet:
E16: (n1-1) x STDEV1 squared
E19: (n2-1) x STDEV2 squared
E22: n 1 ? n 2 -2
E25: 1/n 1 ? 1/n 2
E28:
s.e.
E31:
critical t
E34:
t-test
B37:
Result:
B40:
Conclusion: (see Fig. 5.15 )
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