Students at an elementary school are given a questionnaire that they are asked to return after their parents have completed it. One of the questions asked is, " Do you find that your work schedule makes it difficult for you to spend time with your kids after school"? Of the parents who replied, 85% said "no". Based on these results, the school officials concluded that a great majority of the parents have no difficulty spending time with their kids after school.

Identify the flaw in the study and explain what the individuals designing the study should have done DIFFERENTLY if they wanted to make such strong conclusions.