People are arranged alphabetically by their names and then every 3rd person is chosen for study. The type of sampling is ?
**Core Concept**
Systematic sampling is a type of probability sampling where the sample is selected based on a fixed interval or a fixed number. In this case, every 3rd person is chosen for study, which is a variation of systematic sampling.
**Why the Correct Answer is Right**
The correct answer is because the selection of every 3rd person is based on a fixed interval, which is a characteristic of systematic sampling. This method ensures that every person has an equal chance of being selected, and the sample is representative of the population. In this scenario, the researcher is using a systematic approach to select participants, making it a form of systematic sampling.
**Why Each Wrong Option is Incorrect**
**Option A:** Stratified sampling is incorrect because it involves dividing the population into subgroups or strata and then selecting a sample from each stratum. This method is used to ensure that the sample is representative of the different subgroups within the population, but it is not related to selecting every 3rd person.
**Option B:** Cluster sampling is incorrect because it involves selecting a group or cluster of individuals rather than individual participants. This method is used to study a population that is difficult to access or has a complex structure, but it is not related to selecting every 3rd person.
**Option C:** Convenience sampling is incorrect because it involves selecting participants based on ease of access or availability. This method is often used in pilot studies or small-scale research, but it is not a systematic approach and does not involve selecting every 3rd person.
**Clinical Pearl / High-Yield Fact**
When using systematic sampling, it's essential to ensure that the interval is random and not based on any predictable pattern, such as every 3rd person, to avoid biases and ensure the sample is representative of the population.
**Correct Answer: C. Systematic sampling is a type of probability sampling where the sample is selected based on a fixed interval or a fixed number.