12/31/2022 0 Comments Spss 21 run syntax![]() Steiger 's adjustment consists of replacing both r 12 and r 34 with Mean( r 12, r 34) in the equations for the ir respective standard errors, including the computation of k (see equations 18 and 19 in the original article). Steiger's adjustment when computing PF and ZPF Note that the po oled variance test is the one that corresponds to Potthoff analysi s, which can be carried out if one has the raw data. Users can indicate which version of the test they want by setting input var iable Po ol = 1 (for the pool ed va riance test) or Pool = 0 (for the unequal vari ances test). Our revised code also computes the pooled variance version of the same t-test. We have modified our code to use the correct df for that t-test. Therefore, we ought to have used Satterthwaite degrees of freedom ( df), as is done when using the unequal va riances version of the t-test for comparing two means. We computed the s tandard error of the difference between the two coeff icients using a method that does not assume equal variances. Problem with t-test for comparing two OLS regression coefficients The details of the corrections are also summarized below. The Errata for our article can be downloaded here. Ray also noticed that we had not implemented Steiger's (1 980) adjust ment when computing the standard errors for the PF and ZPF tests. We thank Ray Koopman for noticing that there was a problem with the original version of our t-t est for comparing two independent ordinary least squares (OLS) regression coefficients.
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