What are the main sampling methods in AP Statistics?

Main Sampling Methods in AP Statistics

Sampling methods are techniques used to select a subset (sample) from a population to draw conclusions about the entire group. The goal is to obtain a representative sample to make valid inferences.

Common Sampling Methods

1. Simple Random Sample (SRS):
• Every individual has an equal chance of being selected.
• Stratified Random Sample:
• The population is divided into strata (groups) based on a characteristic, then a random sample is taken from each stratum.
• Cluster Sample:
• The population is divided into clusters (often geographically), some clusters are randomly selected, and all individuals in chosen clusters are sampled.
• Systematic Sample:
• Select every $k$th individual from a list after a random starting point.
• Convenience Sample:

Worked Example: Stratified Random Sample

Problem:
A school has 600 students: 400 in Grade 9 and 200 in Grade 10. You want a sample of 60 students, stratified by grade.

Step 1: Calculate Proportions

Step 2: Allocate Sample Size

Step 3: Randomly Select Within Strata

Takeaways