What term refers to the concept that every individual in the population has an equal chance of being selected for the study?

• A. Quota sampling
• B. Stratified sampling
• C. Equal probability selection (epsem)
• D. Convenience sampling

Answer: (C)

This question tests the idea of equal chances for every individual in the population to be chosen. When each person has the same probability of being selected, the sampling method is called equal probability selection (EPSEM). This is a hallmark of probability-based sampling, typically realized through simple random sampling (or systematic sampling with a random start), where the randomization process ensures no one is more likely to be included than anyone else. EPSEM helps produce unbiased estimates of population characteristics and supports calculating sampling error, assuming a complete and accurate sampling frame and minimal nonresponse bias. The other approaches don’t guarantee equal probability: quota sampling fills fixed numbers from subgroups without random selection, and stratified sampling, while aiming for representation, does not ensure equal chances across the entire population unless the random selection within each subgroup is designed to preserve that equal-probability property. Convenience sampling selects participants based on ease of access, offering no uniform probability of selection.