Final answer:
The researcher is ensuring the random sampling of the sample which means all participants from the population have an equal chance of being chosen for the study, making the sample representative of the population.
Step-by-step explanation:
Whenever a researcher ensures that all participants in a population have an equal chance of participating in a study, he or she is ensuring the random sampling of the sample. Random sampling is a technique where a subset of a population is chosen such that each member has an equal chance of being selected. This method ensures that the sample is representative of the overall population, thus improving the reliability and validity of the study's results. By using random sampling, researchers can obtain a sample that mirrors the characteristics of the population, such as age, gender, socioeconomic status, and other relevant attributes, ensuring that studies can be replicated with consistent outcomes.