For which of the following claims is a representative sample, rather than a biased sample, likely to be essential? For which would a biased sample be acceptable?

a. a political poll predicting who will win a governor's race

b. online readers' ratings of a recently released film

c. estimating school achievement from a sample of test scores from 10 district schools, in order to evaluate which of the 10 schools is the highest achieving

d. evaluating the quality of the day's surfing conditions by asking surfers on the local beach

A representative sample is a small subset of population that accurately reflect the characteristics of large group. It represents the population.

A biased sample is taken from the population of choice and samples are not taken randomly but are selected because of choice. The biased sample does not represent a population.

a. This condition requires a representative sample which will include the entire population of the country or not the chosen population for study.

b. This condition requires a representative sample of large population to derive an opinion about whether the film has acquired success or failure.

c. This condition requires a biased sample as only 10 schools are being compared for achievement on the basis of test scores.

d. This condition requires a biased sample as the day surfing conditions can vary according to preferences of surfers.