## Chapter 5

Sampling and Probability

101

Samples and Their Populations

• Random Sampling
• Convenience Sampling
• The Problem with a Biased Sample
• Random Assignment

Probability

• Coincidence and Probability
• Expected Relative-Frequency Probability
• Independence and Probability

Inferential Statistics

• Developing Hypotheses
• Making a Decision About the Hypothesis

Type I and Type II Errors

• Type I Errors
• Type II Errors

Next Steps: The Shocking Prevalence of Type I Errors

### BEFORE YOU GO ON

• You should understand the difference between a sample and a population (Chapter 1).
• You should know how to measure central tendency, especially the mean (Chapter 4).

102

Lillian and Frank Gilbreth and Their Children Sampling is a way to do things more efficiently, based on principles that Lillian Gilbreth, the “mother of scientific management,” and her husband Frank applied to raising a happy if occasionally chaotic family. Eleven of their twelve children are pictured here.