Residents of a community currently pay a fee for recreational services in their neighborhood, such as tennis courts,running trails, and a pool. To assess whether there is support for raising the fee for the upcoming summer, a randomsample of 50 residents is contacted and asked this question: "Would you support a $10 increase in the recreational feeto support programs for the health and well-being of children in the community ?" Of the 50 residents contacted, 12approved of the fee increase. Which statement describes a likely source of bias present in the survey results?