I have four sets of data grouped by stages (Stage 1-4) with each having their own correlation coefficient. The 4 sets of data has the same dependent and independent variables with 1st n=106, 2nd n=23, 3rd n=89, 4th n=132. My hypothesis is that at stage 4 the correlation would get weaker.
From the numbers alone it supports the idea since the correlation is smaller on the 4th stage than on the 1st, 2nd and 3rd but is there a way to prove it statistically? Or is it just okay to say that there is a weakening in the correlation without having to resort to statistical significance testing? I have read about the Fisher z transform but can it be used to test 4 coefficients? And since I am only comparing the 4th stage to the rest can I just test 1-4 2-4 and 3-4 using Fisher z? Oh and is there a way to do the test using SPSS?