Key ideas

• Researchers usually can't study an entire population because of time, cost, or logistics, so they study a sample instead.
• The more representative a sample is, the more confident researchers can be that their findings apply to the population.
• Sometimes narrowing the population can make it realistic to get a representative sample.
• Sampling bias occurs when some members of a population are more likely to be included than others, which weakens a study's conclusions.
• Random sampling gives every member an equal chance of selection, while convenience sampling is easier but more vulnerable to sampling bias.
• When a sample is representative of the population, the study's findings can be generalized to that population.

Key terms

population

The complete group a researcher wants to learn about.

sample

The group of participants who actually take part in a study.

representative sample

A sample that reflects the characteristics of the larger population.

sampling bias

When some members of a population are more likely to be included in a study than others, making the sample less representative.

random sampling

Selecting participants so every member of the population has an equal chance of being chosen.

convenience sampling

Choosing participants because they are easy to reach, such as friends, classmates, or people nearby.

generalization

The extent to which findings from a sample can be applied to a population.

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