Common Core: S-ID.4
Problem 4 of 45s12-004
Maya scored 88 on a history test with mean 76 and standard deviation 8. Leo scored 85 on a math test with mean 75 and standard deviation 5. Relative to their own tests, who did better?
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Solution walkthrough1:42
- A -score counts how many standard deviations a value is above its mean: value minus mean, divided by SD.
- Maya: points above her mean, and standard deviations.
- Leo: points above his mean, and standard deviations.
- Leo is standard deviations above his mean, Maya only , so Leo did better.
- Traps: and ignore the spread. and divide by the other test standard deviation.