Answer:
a. 68%
b. 99.7%.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 246.8
Standard deviation = 67.2
a. What is the approximate percentage of women with platelet counts within 1 standard deviation of the mean, or between 179.6 and 314.0?
By the Empirical Rule, approximately 68%.
b. What is the approximate percentage of women with platelet counts between 45.2 and 448.4?
45.2 = 246.8 - 3*67.2
448.4 = 246.8 + 3*67.2
Within 3 standard deviations of the mean, so approximately 99.7%.