multiple regression with two dummy variables - calculating difference between groups I am running a multiple regression:
Visits to a tourist attraction = 0 + 1ticket price + 2income + 3 age + 4female + 5local (local vs foreign visitors)
I wonder how to 1) calculate the difference between genders and 2) how to test the equivalence of the regression among local and foreign visitors?
I am new to such analysis and would appreciate your help.
 A: In the model you specified, $\beta_3$ would give you the difference between males and females, conditional on ticket price, income, age and origin. Likewise, $\beta_5$ would give you the conditional difference between locals and foreigners. If the confidence interval of $\beta_5$ is strictly positive or negative, you have a stastistically significant difference between the two groups. As a rule of thumb, you can multiply the standard error of the coefficient by 2. If this is below the absolute value of the coefficient, your result is approx. significant at the 5% level. 
It might be that you are not interested in these conditional means. In that case, you need to remove some of the other variables from the model.
A: Thanks for all for valuable advice. I am now wondering if it would be wrong to create interaction terms not only testing for the equivalence of the regression among local and foreign visitors but also between female and other variables to find the difference between genders?
If I included the interaction terms for female dummy, the model would look like this:
Visits to a tourist attraction = 0 + 1ticket price + 2income + 3age + 4female + 5local + 6ticket price x female + 7income x female + 8age x female + 9local x female
Then the difference between female and male would be B4 + 6ticket price + 7income + 8age + 9local?
Thanks in advance. 
