RESEARCH METHODS HANDBOOK

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Contents	Introduction	Descriptive	Hypothesis	Tables	Appendix

Two Independent Sample Means (Cochran and Cox)
(T-test) Without Homogeneity of Variance

State the Hypothesis

Null Hypothesis (Ho): There is no difference between the mean of one population and the mean of another population.

Alternative Hypothesis (Ha): There is a difference between the mean of one population and the mean of another population.

Ha for 1-tailed test: The mean of one population is greater (or less) than the mean of the other population.

Set the Rejection Criteria Determine the "degrees of freedom"

Determine level of confidence -- alpha (1 or 2-tailed)

Use the t distribution to determine the critical value

Compute the Test Statistic Standard error of the difference between two sample means

Test statistic

Decide Results of Null Hypothesis There is/is not a significant difference between the mean of one population and the mean of another population from which the two samples were obtained.

Example