一、
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval
1992 7,612 11.62 0.0644    5.619 11.49 11.74
2012 7,440 19.80 0.124 10.69 19.56 20.04
combined 15,052 15.66 0.0770 9.442 15.51 15.81
conf
diff -8,183 0.139 -8.455 -7.911 diff = mean(1992) - mean(2012) t = -58.9871
Ho: diff = 0 degrees of freedom = 15050
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000
二、
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval 1992 7,612 15.64 0.0867 7.564 15.47 15.81 2012 7,440 19.80 0.124 10.69 19.56 20.04 combined 15,052 17.69 0.0772 9.471 17.54 17.85 diff -4.164 0.151 -4.459 -3.869
diff = mean(1992) - mean(2012) t = -27.6423
Ho: diff = 0 degrees of freedom = 15050
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000
三、第二题根据通货膨胀率进行了调整，反映了购买力的变化，所以可用利用第二题的结果进行分析。
四、
Mean estimation Number of obs= 3,485
Mean Std.Err. 95% Conf. Interval
ahe 15.69 0.140 15.41 15.96
Mean estimation Number of obs =3,955
Mean Std.Err. 95% Conf. Interval
ahe 23.43 0.179 23.07 23.78
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval
0 3,485 15.69 0.140 8.247 15.41 15.96
1 3,955 23.43 0.179 11.26 23.07 23.78
combined 7,440 19.80 0.124 10.69 19.56 20.04
diff -7.741 0.232 -8.194 -7.287
diff = mean(0) - mean(1) t = -33.4357
Ho: diff = 0 degrees of freedom = 7438
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000
五、
Mean estimation Number of obs= 4,650
Mean Std.Err. 95% Conf. Interval ahe 13.42 0.0909 13.24 13.60
Mean estimation Number of obs= 2,962
Mean Std.Err. 95% Conf. Interval ahe 19.12 0.150 18.82 19.41
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval
0 4,650 13.42 0.0909    6.201 13.24 13.60
1 2,96
2 19.12 0.150 8.177 18.82 19.41
combined 7,612 15.64 0.0867 7.564 15.47 15.81
diff -5.695 0.165 -6.019 -5.371
diff = mean(0) - mean(1) t = -34.4308
Ho: diff = 0 degrees of freedom = 7610
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.0000 Pr(T > t) = 0.0000 Pr(T > t) = 1.0000
六、先分析大学毕业生1992年和2012年的ahe数据
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval 1992 2,962 19.12 0.150 8.177 18.82 19.41 2012 3,955 23.43 0.179 11.26 23.07 23.78 combined 6,917 21.58 0.124 10.28 21.34 21.82 diff -4.311 0.244 -4.790 -3.832
diff = mean(1992)-mean(2012) t = -17.6377 Ho: diff = 0  degrees of freedom = 6915
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.0000 Pr(T > t) = 0.0000 Pr(T > t) = 1.0000
再分析高中毕业生1992年和2012年的ahe数据
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval 1992 4,650 13.42 0.0909    6.201 13.24 13.60 2012 3,485 15.69 0.140 8.247 15.41 15.96 combined 8,135 14.39 0.0802 7.236 14.23 14.55 diff -2.265 0.160 -2.579 -1.951 diff = mean(1992) mean(2012) t = -14.1422 Ho: diff = 0 degrees of freedom = 8133
Ha: diff < 0 Ha : diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(T > t) = 0.0000 Pr(T > t) = 1.0000
七、
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval
0 4,368 22.43 0.164 10.81 22.11 22.75
1 3,244 19.19 0.157 8.935 18.88 19.49
combined 7,612 21.05 0.117 10.18 20.82 21.28
diff    3.240 0.233    2.784    3.697
diff = mean(0) mean(1) t = 13.9050
Ho: diff = 0 degrees of freedom = 7610
Ha: diff < 0 Ha: diff != 0  Ha: diff > 0
Pr(T < t) = 1.0000 Pr(T >t) = 0.0000 Pr(T > t) = 0.0000
Two-sample t test with equal variances
Group Obs Mean Std.Err. Std.Dev. 95% Conf. Interval
0 4,283 20.91 0.173 11.29 20.57 21.24
1 3,157 18.30 0.171 9.606 17.96 18.64 combined 7,440 19.80 0.124 10.69 19.56 20.04 diff    2.606 0.249    2.118    3.094 diff = mean(0)-mean(1) t = 10.4730 Ho: diff = 0 degrees of freedom = 7438 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 1.0000 Pr(T >t) = 0.0000 Pr(T > t) = 0.0000

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