A variable is normally distributed with mean 50 and standard deviation 10. Approximately what percentage of values lie between 30 and 70?
Answer and explanation
Correct answer: C. 95%
- Step 1: The interval is within 2 standard deviations of the mean, which holds about 95% of the values (the 68-95-99.7 rule). Answer: 95%. Why not the others: 82%: uses the wrong standard deviation band. 50%: gives half the distribution. 99.7%: uses three standard deviations.
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