Biases samples are those where some members of the population are not included in the survey. These samples produce biases results.
The statements that could lead to biased results are :
1. Giving a standardized test to a class of at-risk students : Only at risk students are biased samples here.
2. Asking players on a school football team how much they study : The school football team will have a very few students as compared to the whole school.
3. Asking Republicans for their opinion about a Democrat-sponsored bill : The republicans here are a part of all the population that contains democrats, liberals and republicans. So sample is biased.
