Calculate An Independent t-Test
November 5, 2008 by kltangen
Filed under How To Calculate, t-test
Consider the following data:
X Y
8 5
8 3
11 8
14 4
8 7
6 4
4 2
8 5
8 3
11 8
14 4
8 7
6 4
4 2
To calculate an independent t-test, we need the mean and Sum of Squares for each variable. Then we use this formula:
Doing the calculations, we find:
SSx = 63.71
SSy = 27.43
meanX = 8.43
meanY = 4.71
SSy = 27.43
meanX = 8.43
meanY = 4.71
And n for each variable is 7, so the total number of subjects (N) is 14. The degrees of freedom is N -2, so the df for this study = 12.
Inserting the appropriate infuriation into the appropriate slots in the formula, we calculate that t = 2.52
Comparing this to the critical value of 2.18, which we got by looking up the critical value at the .05 alpha level. We used the Critical Values of t table with 12 degrees of freedom.
Since the value we calculated is larger than the book, the t is significant. That is, there is a significant difference between the two groups and they are unlikely to be from the same population.
