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name: <unnamed>
log: C:\Documents and Settings\Michael Rosenfeld\My Documents\newer web pages\soc_meth_proj3\2011_180B_logs\class3.log
log type: text
opened on: 1 Feb 2011, 13:50:35
. use "C:\Documents and Settings\Michael Rosenfeld\Desktop\cps_mar_2000_new.dta", clear
* Note: Our stata log for class 3 didn't have much in it, as we mostly talked about the means and standard deviations document and the class excel file, about the meaning of standard error of the mean and the t-test.
* Below is my simple demonstration that unequal and the equal variance t-test for men's and women's education (for ages 25-34) is basically the same (5.7xxxxx), because the standard deviations of the two educational distributions are so similar that it doesn't matter whether one makes the equal variance assumption or not. Compare to the log from last class, and also to the unequal variance t-tests in my class Excel file.
. ttest yrsed if age>=25 & age<=34, by(sex) unequal
Two-sample t test with unequal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
Male | 9027 13.31212 .0312351 2.967666 13.25089 13.37335
Female | 9511 13.55657 .0292693 2.854472 13.49919 13.61394
---------+--------------------------------------------------------------------
combined | 18538 13.43753 .0213921 2.912627 13.3956 13.47946
---------+--------------------------------------------------------------------
diff | -.2444469 .0428057 -.32835 -.1605438
------------------------------------------------------------------------------
diff = mean(Male) - mean(Female) t = -5.7106
Ho: diff = 0 Satterthwaite's degrees of freedom = 18383.6
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000
. ttest yrsed if age>=25 & age<=34, by(sex)
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
Male | 9027 13.31212 .0312351 2.967666 13.25089 13.37335
Female | 9511 13.55657 .0292693 2.854472 13.49919 13.61394
---------+--------------------------------------------------------------------
combined | 18538 13.43753 .0213921 2.912627 13.3956 13.47946
---------+--------------------------------------------------------------------
diff | -.2444469 .0427623 -.3282649 -.1606289
------------------------------------------------------------------------------
diff = mean(Male) - mean(Female) t = -5.7164
Ho: diff = 0 degrees of freedom = 18536
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000
. log close
name: <unnamed>
log: C:\Documents and Settings\Michael Rosenfeld\My Documents\newer web pages\soc_meth_proj3\2011_180B_logs\class3.log
log type: text
closed on: 1 Feb 2011, 16:27:42
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