Identify the problem with the following study.

An internet poll on a website asks people to indicate whether or not they have a cable TV subscription. 1974 people respond with 847 indicating that they do have a cable TV subscription.

precise numbers

correlation and causality

nonresponse

voluntary response

I think the problem with the following study is the precise numbers.

Though an exact number of correspondents responded to the internet poll survey, the fact that the poll was conducted through the internet means that there is a possibility that these responses came from all over the world. It is not limited to a specific area.