# selection bias

1. ### 2-stage Heckman instrumental variable estimation

Hi Guys, I am working on my thesis. My main regression model is the following: (1) Y=x1*Payment+x2*Country+x3*Industry..... All independent variables are dummy/binary variables. In a next step I divide my sample and construct the following two regression: (2) Y=x2*Country+x3*Industry... =>...
2. ### Selection probability + time variable?

Greetings statisticians, I seek advice regarding a probability of selection. Here is the scenario: I, living in the US, have a music collection totaling 1000 CDs. A friend, living in Southeast Asia, has a collection totaling 2000 CDs. Given that we have similar musical interests yet live in...
3. ### How does sampling reduce selection bias?

Hi everyone, I'm struggling to understand theoretically how sampling reduces selection bias. Take the following example: Supposing there is a population of 1000 people, and 200 of them have an axe to grind (for some reason). These 200 will respond to 100% of surveys. The remaining 800 are...