Tuesday, January 27, 2009

Excel: Paired t-test

I always forget what must be the value of P must be to reject or not to reject the null hypothesis in paired t-test. So lets explain by the example.H0 - null hypothesis - there is no
significant difference
between method A and B
H1 - alternative hypothesis - there is difference
(two tail test)
For example [with 5% (a=0.05) level of significance ]:

Based on the above results I can say that: "since P=0.009103483 and this is lover than a=0.05 (P<0.05), I can claim that":I'm 95% (a=0.05) sure that there is significant
difference between A and B, because (P<0.05).
On the other hand, we can have:

In this case P=0.649507752, and I can claim that:I'm 95% (a=0.05) sure that there is no significant
difference between A and B, because (P>0.05).
Above paired t-test was performed in Excel.

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