Wilcoxon signed ranked test
I run a Wilcoxon test for the folowing data: pretest: 63 75 75 74 65 63 and post test: 70 48 65 60 68 57
I obtained a W of 17 for a p level of 0.219. I used SPSS and Simstat and for the same data, I have a p level of 0.173 for a Z value of 1.362. I have 2 negative ranks and 4 positive. Why the results are so different? When a do a t test the value of t is the same for the three software.