假设检验与样本数量分析②——双样本z、双样本t、配对t检验

样本为何就可以用z检验?正态分布t态分布t分布自由度=1t分布自由度=15t分布自由度=30正态分布正态分布正态分布补充阅读样本↗自由度↗大样本n1和n250(至少大于30)——宗序平《数理统计学及其应用》“n较大时(n>45),可用标准正态分布代替t分布查tα(n)的值,即tα(n)≈Za其中Za为标准正态分布的α分位点。”双样本Z检验假设检验的例子(4)我们有一种陶瓷PTC热敏电阻产品,烧结工序中我们想了解烧结温度为1330℃和解烧结温度为1350℃时,产品阻值是否有差异?两种温度设定下的产品各分别随机抽取55个样本,测量得到电阻值数据如下:大样本n1=n2=5548.155.550.249.752.642.550.953.246.946.349.546.148.052.151.651.450.148.344.754.951.941.247.057.052.150.945.155.547.650.744.851.152.746.453.845.246.748.152.843.847.146.035.340.652.957.555.143.054.652.253.649.647.357.952.01330℃:1#样本电阻值(Ω)52.853.746.854.638.155.250.854.446.447.557.853.553.658.152.552.652.754.563.060.343.541.745.849.352.842.449.559.745.359.346.649.253.046.637.357.058.540.850.343.151.758.943.659.253.049.240.547.652.844.448.647.154.448.961.81350℃:2#样本电阻值(Ω)样本均值:50.77样本标准差:6.18样本均值:49.49样本标准差:4.58