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# Huynh-Feldt epsilon general procedure 1.0

Date Added: August 17, 2013  |  Visits: 238

%function [EpsHF EpsList EpsGG]=GenCalcHFEps(Y,BTFacs,WInFacs,S)%% This will calculate the Geisser-Greenhouse and Huynh-Feldt epsilon value% for the general case when given a univariate dataset with any amount of% between or within subject factors.%% After calling this function, the intention is to multiply the degrees of% freedom for tests in a repeated measures ANOVA by the corresponding% epsilon value given by this code to obtain a corrected p-value. The% F-statistic does not change as a result of this.%% Inputs:% Y- A column vector of the dependent variable (the value% measured) for each data point.% BTFacs- A matrix of between subject factors. Must have the same% number of rows as Y. Each factor is down a different column% of BTFacs, and the value in each row denotes the level of% that factor for each corresponding datapoint in Y. If there% are no between subject factors, input an empty matrix, [].% WInFacs- A matrix of within subject factors. Must have the same% number of rows as Y. Each factor is down a different column% of WInFacs, and the value in each row denotes the level of% that factor for each corresponding datapoint in Y.% S- A column vector of subject numbers corresponding to each% datapoint in Y. Must have the same number of rows as Y. If% left empty, the program assumes all subjects are entered in% the same order for all combinations of factors.%% Outputs:% EpsHF- A row vector of all the possible values for the Huynh-Feldt% epsilon, correspondding to all main effects for ecah within% subject factor, and all interactions of within subject% factors.% EpsList- A cell array of a text list of the effects corresponding to% the positions in EpsHF. For example 'A' means a main effect% for the first (within subject) factor, 'AB' means a 2way% interaction for the first two (within subject) factors,% etc.% EpsGG- The Geisser-Greenhouse epsilon values, in teh same form as% EpsHF.%% The Huynh-Feldt epsilon value is less conservative while maintaining the% proper Type I error rate, which is why the program title focuses on that.% The Geisser-Greenhouse epsilon is calculated first as part of the% process of calculating the Huynh-Feldt value, so I've allowed it to be% optionally returned as well.%% This code follows a procedure described in Huynh(1978), but includes a% modification of the last step, as described in Chen & Dunlap(1994).%% I've tested this with results from SPSS for a couple of sample datasets% I've found in various websites, and it gives results that match% According to what I've seen and read though, SPSS and SAS give results% for EpsHF that are wrong when both between and with-in factors are% present, and thus they slightly differ from the results this program,% although the results for EpsGG are identical. To reproduce the SPSS% results, uncomment line 153. See other comments near there for references% on why I think SPSS/SAS is wrong.%%% References:%% Huynh H. "Some approximate tests for repeated measurement designs",% Psychometrika (1978)%% Chen, RS and Dunlap, WP "A MonteCarlo STudy on the Performance of a% Corrected Formula for eps(tilda) suggested by Lecoutre", Journal of% Educational Statistics (1994)

 Requirements: No special requirements Platforms: Matlab Keyword: Dunlap,  Huynh,  Includes,  Modification,  Procedure,  Results,  Tested Users rating: 0/10