alleryStart learning →A coin is flipped 100 times. The number of heads has a mean of 20 and a standard deviation of 4. About 95 percent of the time the head count lands where?
ABetween 12 and 28
BBetween 16 and 24
CBetween 8 and 32
DBetween 18 and 22
Answer & Solution
Correct answer: A. Between 12 and 28
1. About 95 percent of values lie within two standard deviations of the mean.
2. Two standard deviations here is 2 times 4, which is 8.
3. Stepping down from 20 gives 20 minus 8, which is 12.
4. Stepping up from 20 gives 20 plus 8, which is 28.
5. The range 16 to 24 is one standard deviation wide and covers only about 68 percent.
_Source: OpenStax High School Statistics (CC BY 4.0), section 6.1 The Standard Normal Distribution_
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