Problem-Solving and Data Analysis practice question

Answer: A. It is plausible that the mean floor area of all apartments in the city is between 48 and 52 square metres.

A confidence interval is a plausible range for the POPULATION MEAN. It says nothing about the spread of individual apartments.

Why the other answers are wrong

B. 95% of the apartments in the city have floor areas between 48 and 52 square metres.

Individual apartments vary far more than this; the interval is about the mean, not the spread.

C. Exactly 95% of the apartments in the sample have floor areas between 48 and 52 square metres.

The interval concerns the population mean, not how the sample's individual values are distributed.

D. The mean floor area of all apartments in the city is certainly 50 square metres.

50 is the centre of the interval, but the interval exists precisely because the mean isn't known for certain.

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