The value we are interested in is the difference between the two means, so our point estimate is the value of one mean minus the other, or M 1 minus M 2 . Just like before, this is our observed effect...The value we are interested in is the difference between the two means, so our point estimate is the value of one mean minus the other, or M 1 minus M 2 . Just like before, this is our observed effect and is the same value as the one we place in the numerator of our test statistic.