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Overview of Hypothesis Testing

Laura Lee Johnson

johnslau@mail.nih.gov

Tuesday, October 26, 2004

Objectives

Discuss commonly used terms, e.g.

P-value
Power
Type I and Type II errors

Present a few commonly used statistical tests for
comparing two groups.

Outline

Estimation and Hypotheses
Continuous Outcome/Known Variance

Test statistic, tests, p-values, confidence intervals

Unknown Variance
Different Outcomes/Similar Test Statistics
Additional Information
Conclusions

Statistical Inference

Inferences about a population are made on the basis
of results obtained from a sample drawn from that population.
Want to talk about the larger population from which
the subjects are drawn, not the particular subjects!

What do we Test

Effect or Difference we are interested in

Difference in Means or Proportions
Odds Ratio (OR)
Relative Risk (RR)
Correlation Coefficient

Clinically important difference

Smallest difference considered biologically or clinically
relevant

Medicine: usually 2 group comparison of population
means