9练习题参考答案.ppt

23.425.6.24.024.510 xxn222112212/30091200/13040.9111292 380 4 400 . 1 580479.382 4 9 . 4 1()62320kkkfSff Xf Xf XXffffxfx （1）正态分布）正态分布（2）算术均数与标准差）算术均数与标准差40.91=3.591301.961.96472.34 486.42SxSnXSXSXX可信区间为（，）=(479.38+1.96 3.59,479.38-1.96 3.59)即（，）1.96479.381.9640.91(399.20,559.56)XS1)(2 nXXSnSSX Sx或2.583.292.58 0.44(2.15 4.42)xskg1.963.29 1.96 0.039(3.21 3.37)Xxskg|3.25.237,110 19/1.63/ 10ddtnSn |5.05.303,110 19/2.98/ 10ddtnSn 1212121212| 3.25.0 |1.611.1221010218XXXXXXddtSdnn222()()11.141()()();(A TadbcnTab cd ac bd22()(1830)248403,1 1830bcbcbc本例a+c=120*60%=72a+b=120*50%=60a=120*35%=42