Wilcoxon test with chicken's weight

Use exactRankTests::wilcox.exact:

If x is a weight for example time 0 e.g. chick$weight.0 and y is a weight for example time 2 e.g. chick$weight.2

Then you could do it this way:

With wilcox.test you will get a warning message:

> wilcox.test(c(chick$weight.0, 200), chick$weight.2)$p.value
[1] 6.660003e-14
Warning message:
In wilcox.test.default(c(chick$weight.0, 200), chick$weight.2) :
  cannot compute exact p-value with ties

Use exactRankTests::wilcox.exact() that can handle ties:

t.test(chick$weight.0,chick$weight.2)$p.value
6.660003e-14

exactRankTests::wilcox.exact(c(chick$weight.0, 200), chick$weight.2)$p.value
[1] 5.889809e-18