22.从两个正态总体中分别抽取两个独立的随机样本,它们的均值和标准差如表 7-7 所示。-|||-表 7-7-|||-来自总体1的样本 来自总体2的样本-|||-overline ({x)_(1)}=25 (overline {{x)_(2)}=23}-|||-({S)_(1)}^2=16 ({S)_(2)}^2=20-|||-(1)设 _(1)=(n)_(2)=100, 求 (mu )_(1)-(mu )_(2) 的95%的置信区间。-|||-(2)设 _(1)=(n)_(2)=10, ({sigma )_(1)}^2=({sigma )_(2)}^2, 求 (mu )_(1)-(mu )_(2) 的95%的置信区间。-|||-(3)设 _(1)=(n)_(2)=10, ({sigma )_(1)}^2neq ({sigma )_(2)}^2, 求 (mu )_(1)-(mu )_(2) 的95%的置信区间。-|||-(4)设 _(1)=10, _(2)=20, ({sigma )_(1)}^2=({sigma )_(2)}^2, 求 (mu )_(1)-(mu )_(2) 的95%的置信区间。-|||-(5)设 _(1)=10, _(2)=20, ({sigma )_(1)}^2neq ({sigma )_(2)}^2, 求 (mu )_(1)-(mu )_(2) 的95%的置信区间。l;