Difference between revisions of "User:Regina/MYDrafts3"
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it uses the pooled variance | it uses the pooled variance | ||
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<math>s_P^2 = \frac {(n-1) s_X^2 + (m-1) s_Y^2} {n-1+m-1} </math> | <math>s_P^2 = \frac {(n-1) s_X^2 + (m-1) s_Y^2} {n-1+m-1} </math> | ||
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| + | With | ||
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| + | <math>t = \frac {\left | \overline X - \overline Y \right |}{\sqrt { s_P^2}} \sqrt n</math> | ||
Revision as of 21:40, 31 March 2010
Details
The Student's test is related to the t-distribution. Its density function is
where 
is the Gamma function and 
the parameter degree of freedom.
Paired Samples
If type=1, TTEST calculates the p-value for a paired Student's test. It uses the differences of the pairs. So in this case the data X and Y should have the same count n.
TTEST returns 
OpenOffice.org uses internally the regularized incomplete beta function to calculate this integral.
An empty element or an element of type string is ignored and its corresponding element in the other sample as well. In contrast to other spreadsheet applications OpenOffice.org has no type boolean but treats false as 0 and true as 1.
Unpaired Samples, Equal Variance
If type = 2, TTEST calculates the p-value of a comparison of means for independent samples from populations with equal variance. Besides
it uses the pooled variance
With
==== Unpaired Samples, Not Necessarily Equal Variances
TTEST returns . (3)If type = 3, TTEST calculates the p-value of a comparison of means for independent samples from populations with not necessarily equal variances. With
and
TTEST returns . For an empty element or an element of type Text or Boolean in X the element at the corresponding position of Y is ignored, and vice versa.
