How are probability sampling techniques different from nonprobability sampling techniques?

• A. To use probability sampling, the composition of the population must be known.
• B. When the composition of the population is not known, nonprobability sampling must be used.
• C. Probability sampling requires larger samples.
• D. They are the same.

Answer: (A)

Probability sampling techniques rely on random selection with known inclusion probabilities, which requires having a clear understanding of who belongs to the population and usually a sampling frame. This lets researchers assign each unit a specific chance of being chosen and to estimate how well the sample represents the population, including calculating sampling error. When the population composition isn’t known or a reliable frame isn’t available, you can’t assign accurate probabilities, so probability sampling isn’t feasible and nonprobability methods are typically used instead. That makes knowing the population composition a defining difference between the two approaches. The other statements aren’t accurate: sample size isn’t what defines the distinction, and the two methods are not the same.