题目
A sample mean is computed from a population with a variance of 2.45. The sample size is 40. The standard error of the sample mean is closest to:
选项
A.0.039.
B.0.247.
C.0.387.
答案
B
解析
B is correct. Taking the square root of the known population variance to determine the population standard deviation (σ) results in:「huixue_img/importSubject/1564548696144744448.png」The formula for the standard error of the sample mean (σX), based on a known sample size (n), is:「huixue_img/importSubject/1564548696224436224.png」 B正确。 已知的总体方差的平方根来确定总体标准偏差(σ)结果: σ= 2.45^0.5=1.565 样本均值的标准误差的公式(σx),基于已知样本大小(n),是: σx=σ/(n^0.5) 因此, σx=1.565/(40^0.5) =0.247