一、σ =√7578.9 =87.056878;X▔ = 1147;μ =X▔±σ/√n * Z0.025 = 1147±87.056878/√10 * 1.96 =1147 ± 54;μ的置信区间为 [ 1093,1201 ]小时 。二、1、σ = 0.04;X▔ = 1.257;μ = X▔ ± σ/√n * Z0.025 = 1.257 ± 0.04/√10 * 1.96 = 1.257 ±0.025μ 的置信区间为 [ 1.232,1.282 ] mm 。2、样本方差S^2 = E(x^2) - E(x)^2= ( 1.23^2 + 1.24^2 + …… + 1.28^2 )/10 - 1.257^2 =0.001241S =√0.001241 =0.03522783;μ = X▔ ±S/√n *t0.025(n-1) = 1.257 ± 0.03522783/√10 * 2.26 = 1.257 ± 0.025μ 的置信区间为 [ 1.232,1.282 ] mm 。两问结果相同,说明样本分布与总体分布相似度很高。