Otani and Kishi (A-12) studied seven subjects with diabetic macular edema. They measured the foveal thickness ð Þ mm in seven eyes pre- and post-unilateral vitrectomy surgery. The results are shown in the following table:

Subject Pre-op Foveal Thickness ðmmÞ Post-op Foveal Thickness ðmmÞ

1 690 200 2 840 280 3 470 230 4 690 200 5 730 560 6 500 210 7 440 200 Source: Data provided courtesy of Tomohiro Otani, M.D.

Use the Wilcoxon signed-rank test to determine whether one should conclude that the surgery is effective in reducing foveal thickness. Let a ¼ :05. What is the p value?