Why is my independent t-test different in SPSS or Excel?

Question

I want to compare the output of my simulation model to the observed data in various ways, like using an independent t-test to compare the means. However, when I do the independent t-test in SPSS, I get a different result than the independent t-test in Excel. I don't know why so I don't know which one I should use. Can anybody tell me why the results are different?

Here is the independent t-test in SPSS (with t-value 0,181 and p-value 0,857):

Here is the t-test: Two-Sample Assuming Equal Variances in Excel (also the t-test assuming unequal variances is different than the one in SPSS):

How come you have different n (23 and 24) in the SPSS version? — Tom Sharpe, Feb 10 '22 at 22:58
What theory does Excel base its calculations on and what does SPSS base its calculations on? Are they the same? — Solar Mike, Feb 11 '22 at 05:34

score 2 · Accepted Answer · answered Feb 11 '22 at 07:12

After running the TTest on your original data in SPSS, with the FULL data, I got perfectly matching results from spss and excel (see below).
The problem you had has to do with one case seemingly missing from your "observed" set (as noted by @TomSharpe).
This could be due to a simple error in copying the data to SPSS. In SPSS you had to have the two ranges in the same column - you may have done this manually with an error - in which case you should learn to use restructure commands, namely varstocases, to avoid such mistakes.

On the other hand, if the data is full but still a case seems to be missing from the analysis, you should check if the data is weighted by another variable. Weighted data can change the apparent number of observarions in the analysis, and of course change the results. .

Why is my independent t-test different in SPSS or Excel?

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