Why is a master list of all members of the population important to probability sampling?

• A. To avoid selection bias when sampling
• B. To ensure equal representation of subgroups
• C. To speed up data collection
• D. To simplify data analysis

Answer: (A)

Having a complete master list provides the sampling frame that makes probability sampling possible. In probability sampling, each member must have a known, nonzero chance of being selected, and the selection is determined by a random process. When you have an accurate master list, you can use random methods (like simple random, systematic, or stratified sampling) and compute how far your sample is from the whole population. This leads to unbiased estimates of population characteristics and valid generalizations. If the list is incomplete or inaccurate, some people are left out or counted twice, creating undercoverage or overcoverage and introducing selection bias that skews results. Other options might sound related to speed, representation by design, or ease of analysis, but they don’t address enabling random selection and ensuring representativeness in the way a proper master list does. So the master list is foundational for reducing selection bias and making the probability-based approach work.