1 SOC 3811 Basic Social Statistics

2 Reminder  Hand in your Assignment 4

3 Class overview Compare means of two groups  Dummy variable regression model  Two sample t-test  Group exercise

4 Dummy Regression Model  Do men and women have different wages?   H o : = 0 H a : ≠ 0 For males: Female=0, so the average male wages = For females: Female=1, so the average female wages = The difference between the means of male and females =

5  If → can ’ t reject the null hypothesis The dummy variable has no influence. The means for two groups are the same  If ｜ Z* ｜ ≥ 1.96 or Sig. (p value)≤.05 → reject the null hypothesis The dummy variable does have an influence. The means for two groups are different.

6 T-test  Sampling distribution: the distribution of all possible estimates of the difference in means Sampling distribution of differences in means

7 T-test  How likely is it to draw means with a difference of, if the difference in population means is really 0?  If common, we can ’ t conclude anything  If rare, we can conclude that the population means differ.

8 T-test Ho:Ho: H a :  For males: the average male wages =  For females: the average female wages=  The difference between the means of male and females= =

9  Calculating z/t :  For any two means, the difference will also fall in a certain range. We can guess the range in which it typically falls  one-tail test two-tail test  

10  If → can ’ t reject the null hypothesis The means for two groups are the same.  If ｜ Z* ｜ ≥ 1.96 or Sig. (p value)≤.05 → reject the null hypothesis The means for two groups are different.

11 Dummy variable regression model

12 T- test

13

14

15 Dummy Regression model

16 T-test