Stats #13: Computing an Appropriate Sample Size

One of your most critical choices in designing a research study is selecting an appropriate sample size. A sample size that is either too small or too large will be wasteful of resources and will raise ethical concerns.

This class will provide hands-on computer experience using a Microsoft Excel spreadsheet for sample size calculations. Please bring a copy of a research paper with you to class.

In this class, you will learn how to:

• identify the information you need to produce a power calculation;
• justify an appropriate sample size for your research; and
• examine the sensitivity of the sample size to changes in your research design.

This class does not qualify for IRB Education Credits (IRBECs).

Contents

• Overview of the STATS web pages
• Consulting services that I provide
• Type II error
• Quick sample size calculations
• Three things you need for a power calculation
• Sample size calculations for a binary outcome
• Confidence intervals
• Negative results
• Please fill out an evaluation form