A voluntary study survey
A fictional school posts an optional survey on its student portal. Of the120 respondents,84 report using a study app and36 report not using it. Average quiz scores are higher in the first group. The survey does not randomly assign app use, does not provide earlier quiz scores, and receives no responses from many students. The school wishes to evaluate the app, while a student journalist wants a careful headline. Consider what the collected observations directly establish, what comparisons would strengthen the investigation, and what remains uncertain. The figures describe respondents only; they are not stated to represent all enrolled students. This case provides the entire data summary needed and requires neither an external chart nor a claim that the app actually exists.
1. What percentage of respondents reported app use?
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84/120=0.70, so70% of respondents reported app use. That percentage is not automatically the percentage among all students.
2. Why is a claim that the app caused higher scores unsupported?
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Participation and app use were voluntary, and prior performance or motivation could differ. Compare suitable groups and account for relevant earlier differences before making a causal claim.