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SPSS syntax for Williams test of two correlations on the same people with one variable in common is taken from here.

``` ================================================ .
* File name:   Williams1959.sps .
* Written by:  Bruce Weaver, bwe...@lakeheadu.ca
* Date:        15-May-2012.
* ================================================ .

* SPSS program to compute Williams' (1959) test for
* comparing two correlations with one variable in common.
* The example used here is from Dave Howell's book
* "Statistical Methods for Psychology" (6th Ed., p. 262).
* It assumes the user wants the difference r12 - r13.
* This example reads in only one row of data, but one could
* read in several rows of data, with one test per row.

data list list / r12 r13 r23 (3f5.3) n (f5.0).
begin data
0.80 0.72 0.89 26
end data.

compute #R = (1 - r12**2 - r13**2 - r23**2) +
2*r12*r13*r23.
compute diff = r12 - r13.
compute t = diff *
SQRT( ((n-1)*(1+r23)) /
(2*((n-1)/(n-3))*#R +
((r12+r13)**2/4)*
(1-r23)**3) ).
compute df = n-3.
compute p = cdf.t(abs(t)*-1,df)*2.
formats t p diff (f5.3) / df (f5.0).
list r12 r13 diff t df p. ```

```OUTPUT:

r12    r13  diff     t    df     p
.800   .720  .080 1.361    23  .187

Number of cases read:  1    Number of cases listed:  1 ```

None: FAQ/Will (last edited 2014-03-06 17:36:43 by PeterWatson)