```           HYPOTHESIS TESTS COMPARING TWO POPULATIONS

I.  Comparing the means of two independent populations.
A.  State the null hypothesis.
B.  Choose a statistical test.
C.  Check Assumptions.
1.  Two independent random probability samples.
2.  Interval level measurement of variable being
compared.
3.  Groups defined by catergorical variable with two
categories.
4.  For a z-test, the sampling distribution must be
normal, which can be assumed to be true if each
sample contains 100 or more cases.
5.  If either of the sample sizes is less than 30, a
t-test must be used, requiring the additional
assumptions that:
a.  the populations from which the samples are
drawn are normal.
b.  the variance of the two populations is equal,
if an equal variances t-test is used.
D.  Select an alpha level.
E.  Calculate the test statistic and decide about the null.
1.  Calculate the statistic.
2.  Determine the probability associated with the
statistic.
3.  Compare probability to alpha level.

II.  Comparing means in two dependent (matched, paired) populations.
A.  State the null hypothesis.
B.  Choose at statistical test.
C.  Check Assumptions.
1.  Two dependent random probability samples such that
scores from one can be mathed with scores from the
other.
2.  Interval level of measurement on variable being
compared.
3.  Sampling distribution is normally distributed which
can be assumed if the populations are normally
distributed.
D.  Select and alpha level.
E.  Calculate the test statistic and decide about the null.
1.  Calculate the statistic.
2.  Determine the probability associated with the
statistic.
3.  Compare probability to alpha level.