A research study of 100 patients shows that their calcium levels range from 8.8-15.1 milligrams/deciliter (mg/dL), with a mean ofmg/dL. The calcium levels fall in a normal distribution, with a standard deviation of 1.0 mg/dL. Based on this study, we know that the percentage of calcium values below 10.1 is approximately?
1%
2%
5%
8%
16%
Correct answer
2%
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correct answer: B
In any normal distribution, standard deviations fall in the following manner:
68.2% fall within one standard deviation of the mean, and 95.4% fall within two standard deviations of the mean. With a mean of
and a standard deviation of 1.0, this means that approximately 4.6% of the calcium values lie outside of [10.1, 14.1]. Since one half of these will fall below this range, 4.6/2 = 2.3. Therefore, approximately 2% of the calcium values are below 10.1. (B)