A sample of 400 observations will be taken from an infinite population. The population proportion equals 0.8. The probability that the sample proportion will be greater than 0.83 is（）

From a population of 500 elements，a sample of 225 eleme...

单项选择题From a population of 500 elements，a sample of 225 elements is selected.It is known that the variance of the population is 900.The standard error of the mean is approximately（）

Given the following information：Standar ddeviation=8 Co...

单项选择题Given the following information：Standar ddeviation=8 Coefficient of variation=64% The mean would then be（）

在显著性水平α＝0.05时能否认为方案A和方案B在药品中转时间上存在差异？

问答题在显著性水平α＝0.05时能否认为方案A和方案B在药品中转时间上存在差异？