I have IQ scores and various levels of a different factor that is presumed to influence IQ. Subjects' IQ scores (on average) are different at different levels of this factor. I can show that IQ increases with increasing levels of this factor, but how do I compute the "p for trend" that I commonly read about? Is there more than one way to do this? And is it done automatically in any SPSS procedure? Thanks for any advice on this.