## ISC and Wilcoxon signed rank test [Nonparametrics]

Dear mittyri,

❝ Could you please enlighten my pea-sized brain:

❝ ❝ Method 1:

❝ ❝ Calculate the differences T-R for each subject and do a Wilcoxon signed rank test with these intra-subject differences

❝ For each subject we got one difference (contrast). How to perform the test using only one value for each subject? Don't get your point.

May be you are confused by my writing

❝ ❝ Calculate the differences T-R for each subject

Sorry. But I'm not an English man (but only "een Balina, wa"). One difference for each subject, calculated as above described and analyzed by a Wilcoxon signed rank test (non-parametric analogue of a paired t-test) using of course the intra-subject contrasts of all subjects under study.

Let's take a hypothetical example, 8 subjects, ISC already calculated:
 subj <- c(1,   2,    3,    4,   5,   6,     7,    8) isc  <- c(0, 0.5, -0.5, 0.25, 0.0, 1.0, -0.25, -1.0) tr <- wilcox.test(isc, conf.int = T, conf.level = 0.9, exact=F)
tr$estimate is the point estimate of T-R, tr$conf.int its 90% confidence interval.

exact=F is to avoid warnings
cannot compute exact p-value with ties cannot compute exact p-value with zeroes

If you are interested in an exact solution wich can handle ties and zero's see package exactRankTests or coin.

Regards,

Detlew  Ing. Helmut Schütz 