单项选择题 The empirical rule tells us that approximately of the values cluster within a distance of 1 standard deviation from the mean for a bell-shaped distribution（）

单项选择题 The reason that we prefer the sample standard deviation as our measure of typical variation instead of the sample variance is that（）

单项选择题 The sum of the deviations may be 0.00.To get around this problem，we use the（）of the deviations