The athletic director of a large university is curious about community opinion of a new initiative to open a sports arena for both community members and college students to use. The cost of this initiative will be funded through a county-wide sales tax.
The athletic director went to several different health clubs and asked members there if they would support the initiative. Out of $500$ people surveyed, $374$ said they would support the sports arena.
What is a type of bias present here? Furthermore, is the true population proportion who support this initiative higher, lower, or about the same as the sample proportion?