Starting point is chosen at random and the sample is taken at regular intervals; for example, sample eight houses from 120.

• A. Stratified random sampling
• B. Cluster sampling
• C. Simple random sampling
• D. Systematic random sampling

Answer: (D)

This method involves selecting elements by a fixed pattern. You start at a random point, then choose every k-th item along the list. In this example, with 120 houses and a desired sample of 8, the interval is 120/8 = 15. So you pick a random starting house among the first 15, and then take every 15th house after that (for instance, 7, 22, 37, 52, 67, 82, 97, 112). This spreads the sample across the whole set with minimal setup.

This differs from simple random sampling, where you’d just pick 8 houses at random without a fixed pattern. It also differs from stratified sampling, which would divide the population into groups and sample within those groups, and from cluster sampling, which would select entire groups. The key here is the random start plus a regular interval, which is the hallmark of systematic random sampling.