# Sampling Distribution, Difference between Independent
Means (2 of 5)

Sample n

_{1} scores from the population of people
taking the drug and compute the mean. This mean will be designated as M

_{1}.
Then, sample n

_{2} scores from the population of people not taking
the drug and compute the mean. This mean will be designated as M

_{2}.
Finally compute the difference between M

_{1} and M

_{2}.
This difference will be called M

_{d} where the "d" stands
for "difference." This
is the statistic whose sampling distribution is of interest.

The sampling
distribution could be approximated by repeating the above sampling procedure
over and over while plotting each value of M

_{d}. The resulting

frequency distribution would be an approximation
to the sampling distribution. The mean and the variance of the sampling
distribution of M

_{d} are:

and

.

If

and
n

_{1} = n

_{2}=
n then

.

For the present example,

=
50 - 40 = 10 and

.