In systematic sampling, what could cause an unrepresentative sample?

In systematic sampling, what could cause an unrepresentative sample?

• A. The interval matches a repeating pattern in the population
• B. Random selection of names yields too many females
• C. All units have equal probability
• D. It is too expensive

Answer: (A)

Systematic sampling picks a random starting point and then selects every nth item from a list. If there’s a repeating pattern in the population that matches the chosen interval, the sample can end up over- or under-sampling that pattern and miss other variation. That makes the sample unrepresentative because it isn’t capturing the full diversity of the population. For example, if every sixth unit has a specific characteristic and you take every sixth unit, you’ll disproportionately include that characteristic and under-represent others. The other ideas don’t describe a bias inherent to systematic sampling: random imbalances can occur by chance in any method, equal probabilities are not automatically guaranteed in all systematic samples, and cost is a practical issue rather than a source of bias in representativeness.

Systematic sampling picks a random starting point and then selects every nth item from a list. If there’s a repeating pattern in the population that matches the chosen interval, the sample can end up over- or under-sampling that pattern and miss other variation. That makes the sample unrepresentative because it isn’t capturing the full diversity of the population.

For example, if every sixth unit has a specific characteristic and you take every sixth unit, you’ll disproportionately include that characteristic and under-represent others. The other ideas don’t describe a bias inherent to systematic sampling: random imbalances can occur by chance in any method, equal probabilities are not automatically guaranteed in all systematic samples, and cost is a practical issue rather than a source of bias in representativeness.