Common Core: S-IC.3
Problem 19 of 45s12-019
To test whether a study app raises quiz scores, 60 volunteers are split into an app group and a no-app group. Why should a coin flip, not each student, decide the group?
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Solution walkthrough1:38
- Goal: compare quiz scores with the app to scores without it, so that any gap comes from the app alone.
- If students choose, the keen ones pick the app. The app group is then more motivated before it starts.
- A coin flip for each student spreads keen and less keen students about evenly over both groups.
- Now the groups differ mainly in the app, so a gap in scores can be credited to the app.
- Traps: results for all students need random sampling, hiding the group is blinding, and half get no app.