Re: How does SPSS compute the Bonferroni adjusted alpha used in their >2x2 Chi-square tests?

Posted by Jon Peck on Oct 14, 2016; 5:30pm
URL: http://spssx-discussion.165.s1.nabble.com/How-does-SPSS-compute-the-Bonferroni-adjusted-alpha-used-in-their-2x2-Chi-square-tests-tp5733251p5733257.html

You can get the same result from the CTABLES column proportions test if you specify APA-style significance indication.  In the CTABLES output, you get a bit more explanation.

Note: Values in the same row and subtable not sharing the same subscript are significantly different at p< .05 in the two-sided test of equality for column proportions. Cells with no subscript are not included in the test. Tests assume equal variances.

Tests are adjusted for all pairwise comparisons within a row of each innermost subtable using the Bonferroni correction.

CTABLES now (V24) offers more choices and information.

You can choose between Bonferroni and Benjamini-Hockberg FDR,

and you can get the actual significance levels if you choose a separate table for the results.

You can also specify the significance levels you want and can get non-APA style indicators,

which I find more understandable.

On Fri, Oct 14, 2016 at 10:41 AM, Emet Schneiderman <[hidden email]> wrote:

You can find the adjustment formula in the Algorithms documentation under
CROSSTABS.  It is based on the subtable in the column proportions test.

Jon - Thanks for pointing me to the documentation.  If I understand it
correctly, the Bonferroni corrections are computed on a row by row basis,
and do not account for the total number of rows in the contingency table
(i.e., treated as independent). For example with a 6x4 contingency table (6
response levels in the rows and 4 groups in columns),  there are 6 possible
pairwise comparisons per row, so the adjusted alpha level (threshold) would
be 0.00833, (.05/6).  Is this your understanding?



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