Problem-Solving and Data Analysis practice question

Answer: A. Sampling variability: different random samples from the same population naturally give somewhat different estimates.

Each random sample contains different households, so its mean lands a little differently. That expected spread is exactly what a margin of error describes.

Why the other answers are wrong

B. One of the samples must have been selected in a biased way.

Random samples differ even when both are drawn correctly; a difference of this size is no sign of bias.

C. The city's mean household size changed between the two studies.

Nothing suggests the population changed; sampling alone accounts for a small gap.

D. One of the researchers must have made an arithmetic error.

An error is possible but not needed to explain a gap this small between two random samples.

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