R T-Test from N/Mean/SD

r statistics hypothesis-test
Xodarap picture Xodarap · Apr 3, 2011 · Viewed 18.2k times · Source

I know that if I have a set of data, I can run t.test to do a T test. But I only know the count, mean and standard deviation for each set. I'm sure there must be a way to do this in R, but I can't figure it out. Any help?

Answer

Ari B. Friedman picture Ari B. Friedman · Apr 3, 2011

Using the formula for t-tests with unequal variance and unequal sample sizes. Note that this is for an unpaired t-test.

t.test.fromSummaryStats <- function(mu,n,s) {
   -diff(mu) / sqrt( sum( s^2/n ) )
}

mu <- c(.1,.136)
n <- c(5,7)
s <- c(.01,.02)
t.test.fromSummaryStats(mu,n,s)

Related questions

How to write a loop to run the t-test of a data frame?

I met a problem of running a t-test for some data stored in a data frame. I know how to do it one by one but not efficient at all. May I ask how to write a loop to do …

Read More
Kolmogorov-Smirnov test

I'm using the R function ks.test() to test the Uniform distribution of the R random number generator. I'm using the following code: replicate(100000, ks.test(runif(n),y="punif"). When n is less than or equal to 100 it works, …

Read More
doing t.test for columns for each row in data set

I have a set of data x which consists of 12 columns and 167 rows. The first column is compound Id for each row. I want to run a t.test for 3 column as one group and the other 3 groups as the …

Read More