Selection bias here is due to the fact that "heavy alcohol use" (the explanatory variable of interest) is not randomly assigned to the treatment group. Since the "liver cirrhosis" patients chose to drink alcohol, they are different from the control group in observable and unobservable ways. Here, the treatment group could be more likely to be of a certain race, which makes them more prone to the disease (and also alcohol consumption). They could also be more likely to take other types of drugs which damage liver. Also, being these types of patients could lead to depression which leads to alcohol consumption (this is the simultaneity endogeneity problem).
Selection bias here is due to the fact that "heavy alcohol use" (the explanatory variable of interest) is not randomly assigned to the treatment group. Since the "liver cirrhosis" patients chose to drink alcohol, they are different from the control group in observable and unobservable ways.
Here, the treatment group could be more likely to be of a certain race, which makes them more prone to the disease (and also alcohol consumption). They could also be more likely to take other types of drugs which damage liver. Also, being these types of patients could lead to depression which leads to alcohol consumption (this is the simultaneity endogeneity problem).
helpful but is still a bit confused. Thank you for the explanation.
Maam I would really like to get your email
poor explaination complete wastes of time