[Rasch] DIF and multiple comparisons - BH method

renselange at earthlink.net renselange at earthlink.net
Wed Feb 8 03:33:35 EST 2006


I use the algorithms for the t distribution in Vetterling et al. (Numerical Recipes book). If remember well, these are sufficiently precise (to within 10E-6).

Rense Lange

-----Original Message-----
>From: Randy and Shelley MacIntosh <srmac at saber.net>
>Sent: Feb 7, 2006 2:10 AM
>To: rasch at acer.edu.au
>Subject: [Rasch] DIF and multiple comparisons - BH method
>
>Mike:
>This would be a welcome addition to Winsteps. But you will have to carry
>out the computation of the t- and p-values to 4 or 5 (or more) decimal
>places to permit its use when you have many items and groups.
>
>
>
>To: rasch at acer.edu.au
>From: "Mike Linacre (RMT)" <rmt at rasch.org>
>In-Reply-To: <43e7782e.3ec4.0 at saber.net>
>Mime-Version: 1.0
>
>Thank you, Randy and Fred,
>
>The Benjamini, Y. & Hochberg, Y. (1995) method for multiple comparisons
>appears to be:
>(1) Compute individual p-values for each of the N hypothesis tests as
>though each was the only one.
>(2) Sort the N p-values by size ascending, n=1,N, so that p(1) is the
>smallest, and p(N) is the largest
>(3) Starting from p(N) downwards, look down for the first p(n) which is
>less than or equal to (n/N) * 0.05 (or your chosen significance level)
>(4) Tests 1 to n are classified as significant.
>
>Is this correct? Have any useful modifications been proposed? This seems
>easy to implement in software, which I may well do.
>
>Thanks again,
>
>Mike L.
>
>Mike Linacre
>Editor, Rasch Measurement Transactions
>rmt at rasch.org www.rasch.org/rmt/ Latest RMT: 19:3 Winter
>
>
>
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