Introduction to Sampling (College Board AP® Statistics)

Introduction to Sampling

What are populations and samples?

• A population is the set of all the possible elements (items / subjects / individuals) that you could study

• A sample is a smaller subset of the population that you choose to study

  • This means the sample size, , is smaller than the population size,

• You can use a sample to try to learn about the population

  • This is called generalizing

What does sampling with or without replacement mean?

• When selecting elements from the population to use in a sample

  • sampling with replacement means elements can be selected more than once

  • sampling without replacement means elements can only be selected once

What does it mean for a sample to be representative?

• A sample is representative of its population if the elements in it reflect similar patterns and behaviors to the population

  • One way to make a sample representative is to randomly select its elements from the population

What is a census?

• A census is when you study the entire population

When can I use samples to make conclusions about populations?

• You can only generalize conclusions from samples to their populations if the sample has been randomly selected

  • or the sample is representative in some other way