Question

Cheryl wants to find the number of hours seventh-graders do homework each week. There are 297 boys and girls in seventh grade. If Cheryl randomly surveyed 50 girls in the entire school to find the number of hours seventh-graders do homework each week, describe why she would get a biased sample.

Answer 1

Explanation:

Surveying 50 girls would include other grades outside of seventh grade and would not include boys. This would not be a representative sample of the population and would lead to invalid results.

Answer 2

There are a total of 297 students in the 7th grade. Rough estimates would say that about half of that number are boys and half are girls. Asking only 50 random girls would be biased because not only would it not be all of the girls (the number of girls would be around 148 or 149) but it would also be ignoring the roughly 148 to 149 boys there are on estimate. The sample would be biased because it would be ignoring the opinions of more than half the seventh grade.