1. SAMPLE SIZE DETERMINATION
Dr. M. H. Rahbar
Professor of Biostatistics
Department of Epidemiology
Director, Data Coordinating Center
College of Human Medicine
Michigan State University

2. Important Statistical Terms
Population: A set which includes all measurements of interest to the researcher
Sample: Any subset of the population
Parameter of interest: The characteristic of interest to the researcher in the population is called a parameter

3. INFERENTIAL STATISTICS
Estimation: This includes point and interval estimation of certain characteristics in the population(s) (e.g., Means, proportions)
Testing Hypothesis about population parameter(s) based on the information contained in the sample(s)

4. Confidence Intervals for population Mean, µ
95% C.I. For , when n30, is

5. Bound on the error of estimation for mean, µ

6. Confidence Intervals for Prevalence of a disease in a population (or Proportion P) 95% C.I. For Prevalence P is

7. Bound on the error of estimation for Proportion, P

8. Minimum Required Sample Size

12. QUESTION: Do persons with the disease have higher blood levels of “factor X” than those without disease?

14. Risk Factors for Myocardial Infarction (MI)
Null Hypothesis: There is no association between hypertension and Myocardial Infarction, or P1=P2, where P1 and P2 are the prevalence of hypertension among cases and controls respectively.
Alternative Hypothesis: There is an association between hypertension and Myocardial Infarction, P1P2.

20. Sample size determination for a 1:1 case control Ratio
A study with 250 cases, 250 controls will safely detect risk factors with an odds ratio of three or more, unless they are extremely common or extremely uncommon
We have a good chance of detecting factors with an odds ratio of two to three, providing their prevalence in the source population is between about 20% and 70%.

21. Sample size determination for a 1: k case control Ratio
When it is difficult to recruit sufficient cases during the intended study period, the power may be increased by selecting more than one control per case.
For details you may want to see standard Epidemiology textbooks.