Bootstrapping to compare two groups

Question

In the following code I use bootstrapping to calculate the C.I. and the p-value under the null hypothesis that two different fertilizers applied to tomato plants have no eff

Answer 1

Following John, I think the appropriate way to use bootstrap to test if the sums of these two different populations are significantly different is as follows:

x <- c(1.4,2.3,2.9,1.5,1.1)
y <- c(23.7,26.6,28.5,14.2,17.9,24.3)


b_x <- boot(x, sum, R = 10000)
b_y <- boot(y, sum, R = 10000)

z<-(b_x$t0-b_y$t0)/sqrt(var(b_x$t[,1])+var(b_y$t[,1]))
pnorm(z)

So we can clearly reject the null that they are the same population. I may have missed a degree of freedom adjustment, I am not sure how bootstrapping works in that regard, but such an adjustment will not change your results drastically.