Date: Mon, 26 Sep 2005 14:39:10 +0100
ReplyTo: Margaret MacDougall <margmacd@talk21.com>
Sender: "SPSSX(r) Discussion" <SPSSXL@LISTSERV.UGA.EDU>
From: Margaret MacDougall <margmacd@talk21.com>
Subject: Clarification on linear trend test
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Dear SPSS users
I would be grateful for a clarification on what test is actually being assumed on selecting the SPSS option to choose 'Linear trend to factor levels' under 'Comparing Factor Levels' when carrying our a Kaplan Meier Analysis. Previously (through reading publications) I had assumed that this was the ChiSquare test for a linear trend which one can equally well implement using the SPSS Crosstabs procedure for running a ChiSquare test of association. However, the two tests do not deliver the same pvalues. The (albeit naive) reader using the relevant dialogue box options for a Kaplan Meier analysis is led to assume by the way the options are presented that they are performing a logrank test for a linear trend. Does such a test exist and if so, could someone kindly provide a reference.
On a related note, if the two tests (ChiSquare test for linear trend and 'Logrank test for linear trend') are distinct, I would be interested to learn which is the superior one in testing for monotonicity of gradient across different severity categories of a factor when predicting mortality.
Many thanks
Margaret

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