Posted by
Margaret MacDougall on
Dec 13, 2006; 6:41pm
URL: http://spssx-discussion.165.s1.nabble.com/Linear-trend-test-when-using-logistic-regression-model-tp1072347p1072351.html
Dear Marta
Thank you very much for the clarification. I shall try to get a copy of the book that you recommend.
Best wishes
Margaret
Marta García-Granero <
[hidden email]> wrote:
Hi Margaret
Back from short holidays...
MM> I take it that this test allows you to adjust for the other
MM> factors in the model so as to measure the strength of the
MM> independent linear relationship between a given factor and the
MM> dependent variable.
Answer: Yes
MM> Could somebody please guide me to a reference which explains the
MM> calculations involved in this particular version of the chi-square
MM> test of association.
If you want to know more on polynomial contrasts, check specialised
books, like: Maxwell & Delaney "Designing Experiments and Analyzing
Data" Lawrence Erlbaum Associates.
If you Google a bit using this search key: "Polynomial contrasts
logistic regression", you will se that it is widely used in
experimental research to test for linear and non linear trends.
This table was extracted from that book:
**********************************************************
* COEFFICIENTS OF ORTHOGONAL POLYNOMIALS *
**********************************************************
* K Trend Coefficients, c(i) *
* ------------------------------------------------------ *
* 3 Linear -1 0 1 *
* Quad 1 -2 1 *
* ------------------------------------------------ *
* 4 Linear -3 -1 1 3 *
* Quad 1 -1 -1 1 *
* Cubic -1 3 -3 1 *
* ------------------------------------------------ *
* 5 Linear -2 -1 0 1 2 *
* Quad 2 -1 -2 -1 2 *
* Cubic -1 2 0 -2 1 *
* Quartic 1 -4 6 -4 1 *
* ------------------------------------------------ *
* 6 Linear -5 -3 -1 1 3 5 *
* Quad 5 -1 -4 -4 1 5 *
* Cubic -5 7 4 -4 -7 5 *
* Quartic 1 -3 2 2 -3 1 *
* Quintic -1 5 -10 10 -5 1 *
* ------------------------------------------------ *
* 7 Linear -3 -2 -1 0 1 2 3 *
* Quad 5 0 -3 -4 -3 0 5 *
* Cubic -1 1 1 0 -1 -1 1 *
* Quartic 3 -7 1 6 1 -7 3 *
* Quintic -1 4 -5 0 5 -4 1 *
* ------------------------------------------------ *
* 8 Linear -7 -5 -3 -1 1 3 5 7 *
* Quad 7 1 -3 -5 -5 -3 1 7 *
* Cubic -7 5 7 3 -3 -7 -5 7 *
* Quartic 7 -13 -3 9 9 -3 -13 7 *
* Quintic -7 23 -17 -15 15 17 -23 7 *
* ------------------------------------------------ *
* 9 Linear -4 -3 -2 -1 0 1 2 3 4 *
* Quad 28 7 -8 -17 -20 -17 -8 7 28 *
* Cubic -14 7 13 9 0 -9 -13 -7 14 *
* Quartic 14 -21 -11 9 18 9 -11 -21 14 *
* Quintic -4 11 -4 -9 0 9 4 -11 4 *
* ------------------------------------------------ *
* 10 Linear -9 -7 -5 -3 -1 1 3 5 7 9 *
* Quad 6 2 -1 -3 -4 -4 -3 -1 2 6 *
* Cubic -42 14 35 31 12 -12 -31 -35 -14 42 *
* Quartic 18 -22 -17 3 18 18 3 -17 -22 18 *
* Quintic -6 14 -1 -11 -6 6 11 1 -14 6 *
* ------------------------------------------------------ *
**********************************************************
* Extracted from Table A.10 of Maxwell & Delaney "Designing
Experiments and Analyzing Data" Lawrence Erlbaum Associates.
--
Regards,
Dr. Marta García-Granero,PhD mailto:
[hidden email]
Statistician
---
"It is unwise to use a statistical procedure whose use one does
not understand. SPSS syntax guide cannot supply this knowledge, and it
is certainly no substitute for the basic understanding of statistics
and statistical thinking that is essential for the wise choice of
methods and the correct interpretation of their results".
(Adapted from WinPepi manual - I'm sure Joe Abrahmson will not mind)
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