Practice question · Multiple choice
Two classes both average 70%. One has a standard deviation of 3, the other of 20. What does a teacher learn from the second number that the mean concealed?
Hints
- Sketch both distributions. Where are the students actually sitting in each?
- Ask which class can be taught with a single lesson plan.
Show the answer
A. Whether 70 describes the class or nobody in it
Why
Same centre, different classroom. A spread of 3 means one lesson fits everyone; a spread of 20 means the average describes a gap rather than a person, and half the room needs something else. Reporting a mean with no spread hides exactly the thing that decides what to do.
Practise Descriptive Statistics
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