We have two groups and we want to figure out the likelihood of being correct.
Are these two groups identical?
 1. Calculate the difference in the means
 We use eqn 2.1 to calculate and and
subtract, getting
.
 2. Calculate the estimated variance of this difference
 We use eqn. 2.11 to do get
.
 3. Form t

.
 3. Calculate likelihood
 The number of degrees of freedom , is one less than the total number of data
points, that is it equals . With that and t, we feed it into a
program, or use a table to calculate the area under the curve as pictured in
fig. 2.7.
 4. Verdict
 If this area is less than our cutoff for significance, say we reject
and say the difference is statistically significant. Otherwise, we can't
reject .
Keywords
 how to figure probability problems.
josh
20101020
 
