For the following problems, select the best response:

(a) A statistic is said to be unbiased if A. the survey used to obtain the statistic was designed so as to avoid even the hint of racial or sexual prejudice. B. the mean of its sampling distribution is equal to the true value of the parameter being estimated. C. it is used for only honest purposes. D. both the person who calculated the statistic and the subjects whose responses make up the statistic were truthful.

(b) Sampling variation is caused by A. changes in a population parameter that cannot be predicted. B. changes in a population parameter from sample to sample. C. systematic errors in our procedure. D. random selection of a sample.

(c) The sampling distribution of a statistic is A. the extent to which the sample results differ systematically from the truth. B. the probability that we obtain the statistic in repeated random samples. C. the mechanism that determines whether or not randomization was effective. D. the distribution of values taken by a statistic in all possible samples of the same size from the same population.