In the context of a randomized block experiment, let Wi denote the sample rank sum associated with the ith population treatment. Show that the Friedman’s test statistic can be re-expressed as

Use a rank-sum test (as did the article’s authors) to determine if PEGPH20 yields higher vessel patency than the standard treatment at the .05 level. Would you also reject the null hypothesis at the .01 level? Comment on these results in light of the fact that every PEGPH20 measurement is higher than every standard-treatment measurement.

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Fr= 12 I(I+1)J 12 I(I+1)J WW i=1 ( W²-3 (I + 1)J J(+1)) 2 Wi 2