The two sample
ttest is a
hypothesis test
used to to compare the means of
two reasonably small (30 or less) samples
to see if it is feasible that they come
from the same population. The hypothesis
is:
H_{0} the population means are
equal
H_{1} the popular means are different
The test is:
Step 1: calculate the pooled standard deviation:
Step 2: calculate the t statistic:
The degrees
of freedom:

sample means 
n_{1}, n_{2} 
sample sizes 
s_{1}, s_{2} 
sample standard deviations 
ν

degrees of freedom 
See also Paired
tTest and One
Sample tTest
