单选题 An increase in which of the following items is most likely to result in an increase in the width of the confidence interval for the population mean?
【正确答案】 B
【答案解析】[解析] 可靠因子的增长将使总体平均值的置信区间相应扩大，而样本空间和自由度的增长则使总体平均值的置信区间相应缩小。因此，本题的正确选项为B。