正态性检验:H:资料服从正态分布ⅴsH:资料偏态分布 每一组资料正态性检验 ktest x if group==0 Skewness/Kurtosis tests for Normality Jo1 Variable Pr(Skewness) Pr(Kurtosis) adj chi2(2) Prob>chi2 0.927 0.326 1.0 0.5926 sktest x if group==l s/Kurtosis tests for Normality Variable Pr(Skewness) Pr(Kurtosis) adj chi2(2) Prob>chi2 0.474 0.675 0.73 0.6948 P值均大于α,因此可以认为两组资料都服从正态分布 H:p1=μ2vsH1:μu1≠2 =0.05 ttest x, by(group) Two-sample t test with equal variances oup Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] 89.081.8229289.1146485.3176692.84234 25101.521.9009829.50491197.59657105.4434 combined 1.57745611.154392.1299898.47002 diff I -12.442.633781 17.73557-7.144429 Degrees of freedom: 48 Ho: mean (0)- mean (1)=diff =0 Ha: diff< 0 Ha: diff=0 Ha: diff>0 4.7232 t=-4.7232 P<t=0.0000 P>|t=0.0000 =1.0000正态性检验：H0：资料服从正态分布 vs H1：资料偏态分布 α=0.05 每一组资料正态性检验 sktest x if group==0 Skewness/Kurtosis tests for Normality ------- joint ------ Variable | Pr(Skewness) Pr(Kurtosis) adj chi2(2) Prob>chi2 -------------+------------------------------------------------------- x | 0.927 0.326 1.05 0.5926 . sktest x if group==1 Skewness/Kurtosis tests for Normality ------- joint ------ Variable | Pr(Skewness) Pr(Kurtosis) adj chi2(2) Prob>chi2 -------------+------------------------------------------------------- x | 0.474 0.675 0.73 0.6948 P 值均大于α，因此可以认为两组资料都服从正态分布 H0：μ1＝μ2 vs H1：μ1≠μ2 α=0.05 ttest x,by(group) Two-sample t test with equal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- 0 | 25 89.08 1.822928 9.11464 85.31766 92.84234 1 | 25 101.52 1.900982 9.504911 97.59657 105.4434 ---------+-------------------------------------------------------------------- combined | 50 95.3 1.577456 11.1543 92.12998 98.47002 ---------+-------------------------------------------------------------------- diff | -12.44 2.633781 -17.73557 -7.144429 ------------------------------------------------------------------------------ Degrees of freedom: 48 Ho: mean(0) - mean(1) = diff = 0 Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 t = -4.7232 t = -4.7232 t = -4.7232 P < t = 0.0000 P > |t| = 0.0000 P > t = 1.0000