21.Suppose that X is a discrete random variable taking on the values of 0, 1 and 2, and the corresponding probability function f(·) is such that 2f(0)=f(1)=f(2). Then, the expected value of X is (A)1/5 (B)2/5 (C)4/5 (D)1 (E)6/5

5.What is meant by the term "90% confident" when constructing a confidence interval for a mean? (A)If we took repeated samples, approximately 90% of the samples would produce the same confidence interval. (B)If we took repeated samples, approximately 90% of the confidence intervals calculated from those samples would contain the sample mean. (C)If we took repeated samples, approximately 90% of the confidence intervals calculated from those samples would contain the true value of the population mean. (D)If we took repeated samples, the sample mean would equal the population mean in approximately 90% of the samples. (E)We are 90% confident that 90% of the data falls within the confidence interval.

21.Suppose that X is a discrete random variable taking on the values of 0, 1 and 2, and the corresponding probability function f(·) is such that 2f(0)=f(1)=f(2). Then, the expected value of X is
(A)1/5
(B)2/5
(C)4/5
(D)1
(E)6/5

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