Is it possible to use t.test() do t-test when I have only two means, sample size, two standard deviations ? (no raw data).
When you type 't.test.default', you get the source code of the t.test function.
If you are conducting a t.test with var.equal=T, paired=F, alternative=two.sided,
the following commands are executed:
df <- nx + ny - 2
v <- ((nx - 1) * vx + (ny - 1) * vy)/df
stderr <- sqrt(v * (1/nx + 1/ny))
tstat <- (mx - my - mu)/stderr
pval <- 2 * pt(-abs(tstat), df)You could write your own function taking nx, mx, vx and ny, my and vy as args.
(vx=var(x))
my.t.test <- function (nx,mx,vx,ny,my,vy) {
df <- nx + ny - 2
v <- ((nx - 1) * vx + (ny - 1) * vy)/df
stderr <- sqrt(v * (1/nx + 1/ny))
tstat <- (mx - my)/stderr
pval <- 2 * pt(-abs(tstat), df) cat("df=",df)
cat("\nT=",tstat)
cat("\np=",pval)
}Christophe Pallier www.pallier.org
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