Date: Thu, 22 Feb 1996 18:22:19 GMT m.voeten@ped.kun.nl "SPSSX(r) Discussion" Rinus Voeten K.U. Nijmegen Simultaneous confidence intervals in MANOVA

The MANOVA procedure in SPSS (version 6.1 for Windows) can provide simultaneous confidence intervals for parameter estimates using the Bonferroni-procedure or the Scheffi-procedure. In some cases, however, at first sight SPSS seems to give the wrong output. An example is given below, using the Bonferroni-procedure. For the first design the intervals were correctly adjusted. But for the second design individual 95%-confidence intervals were outputted, though the output claims these are joint univariate Bonferroni intervals. One might get trapped here, because the output does not make clear to what set of contrasts the simultaneous confidence intervals apply. Using partitioned contrasts on the design statement, apparently, changes the definition of the "family" for which the family-wise error-rate is controlled. It took me some time to realize that. So, if I understand it well, the simultaneous confidence intervals are determined for the sets of contrasts specified in the design statement. These might be main effects or interactions, but also subsets of contrasts belonging to a particular factor. In the second design there is just one contrast for each partition, and thus there can be no Bonferroni correction. Am I correct?

-> MANOVA -> score BY conditie(1 4) -> /CONTRAST (conditie) = SPECIAL (1 1 1 1 -> -3 1 1 1 -> 0 -2 1 1 -> 0 0 1 -1 ) -> /PRINT PARAM(ESTIM) -> /METHOD=UNIQUE -> /ERROR WITHIN+RESIDUAL -> /CINTERVAL= JOINT(.95) UNIVARIATE(BONFER) -> /DESIGN -> /DESIGN conditie(1) conditie(2) conditie(3) .

* * * * * * A n a l y s i s o f V a r i a n c e -- design 1 * *

Estimates for SCORE --- Joint univariate .9500 BONFERRONI confidence intervals

CONDITIE

Parameter Coeff. Std. Err. t-Value Sig. t Lower -95% CL- Upper

2 10.8333333 1.74786 6.19806 .00000 6.54296 15.12371 3 2.66666667 1.23592 2.15763 .03449 -.36709 5.70042 4 .666666667 .71356 .93428 .35346 -1.08487 2.41820

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

* * * * * * A n a l y s i s o f V a r i a n c e -- design 2

Estimates for SCORE --- Joint univariate .9500 BONFERRONI confidence intervals

CONDITIE(1) Parameter Coeff. Std. Err. t-Value Sig. t Lower -95% CL- Upper 2 10.8333333 1.74786 6.19806 .00000 7.34554 14.32113

CONDITIE(2) Parameter Coeff. Std. Err. t-Value Sig. t Lower -95% CL- Upper 3 2.66666667 1.23592 2.15763 .03449 .20042 5.13291

CONDITIE(3) Parameter Coeff. Std. Err. t-Value Sig. t Lower -95% CL- Upper 4 .666666667 .71356 .93428 .35346 -.75722 2.09055

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