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Holm-Sidak t-test

25 Oct 2006 (Updated 19 Nov 2008)

Holm-Sidak t-test for multiple comparisons

File Information
Description	As you know, the Student t-test can be used only to compare two groups. When you have k groups you can't use a t-test for each couple because, if you have fixed alpha=0.05 for each t-test, there is a probability of k*0.05 to find a difference when it isn't (Bonferroni inequality). The Holm-Sidak test is a step-down "recursive reject", because it applies an accept/reject criterion on a sorted set of null hypothesis, starting from the lower p-value and going up to the acceptance of null hypothesis. For each comparison, the alpha value is set according to Sidak correction of Bonferroni inequality. Statistics Toolbox is required because this function use TCDF function.
Required Products	Statistics Toolbox
MATLAB release	MATLAB 6.5 (R13)

Tags for This File
Everyone's Tags	holm, multiple ttest, probability(2), sidak, statistics(2)
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Comments and Ratings (3)
19 Dec 2007	nick from belgium	sorry but this does not explain anything to someone who is crap at stats.
21 Dec 2007	Giuseppe Cardillo	I think that my explanation is very simple and if "someone is crap at stats" he never will search this file.
27 Dec 2007	Gilbert Norrell	This file is similar to multcompare matlab function, but provides much more clear outputs.

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Updates
26 Oct 2006	m-lint improvements
30 Oct 2006	Error handling and calculation improvements
31 Oct 2006	Logical indexing implemented
17 Jun 2008	Correction to avoid error generation when more comparisons have the same p-value.
24 Sep 2008	Improvement in input error handling
12 Nov 2008	Changes in help section
19 Nov 2008	logical indexing improved

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