Final answer:
The student's survey method was not a controlled experiment and may be subject to bias, as it included younger siblings and potentially lacked random sampling.
Step-by-step explanation:
The student wanting to determine how his classmates feel about school did not conduct a well-designed, controlled experiment. Surveys can provide valuable information when done correctly, but the inclusion of younger siblings means the survey now includes data from a population that is not restricted to his classmates. Furthermore, if the survey was not conducted with a random sample, it could suffer from selection bias, which can skew results. For an accurate reflection of the classmates' feelings, the survey should target a specific population—in this case, the student's classmates—and ideally should employ random selection to minimize potential biases. Moreover, a survey is a form of an observational study, not a controlled experiment, as it does not involve manipulating variables and observing the outcome.