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What is the appropriate test statistic for constructing confidence intervals for the population mean of a nonnormal distribution when the population variance is unknown and the sample size is large (n ≥ 30)? A. The z-statistic at α with n degrees of freedom. B. The t-statistic at α with 29 degrees of freedom. C. The t-statistic at α/2 with n degrees of freedom. D. The z-statistic or the t-statistic. |