What is a systematic sample?

A systematic sample is defined as a method where members of a population are selected at regular intervals. This approach starts with selecting a random point in the population, and then every nth member is chosen from that point forward. For example, if you wanted to take a systematic sample of a population of 100 individuals, you might randomly select a starting point, say the 3rd individual, and then choose every 10th individual afterward (3rd, 13th, 23rd, etc.).

This method is efficient and straightforward, allowing for a representative sample when the population is homogeneous. It also avoids bias that might arise in other sampling methods, as every member has a systematic chance of being included based on the interval selected.

The other choices do not accurately represent the characteristics of a systematic sample: while random selection can play a role in starting the process, the key feature of systematic sampling is the regular interval selection, which is not based purely on randomness or convenience. Additionally, systematic sampling can be applied to populations of any size, not just large ones.