Answer:
2.3%
Step-by-step explanation:
Imagine a standard normal curve with mean at 100 mg. One standard deviation above the mean would be 110 mg; two standard deviations 120 mg.
Draw a vertical line through x = 120. To answer this question, we must find the area under the curve to the left of x = 120 and then subtract this result from 1.00:
Using a calculator with probability distribution functions built in, we find the area to the left of x = 120 as follows:
normcdf(-100,120,100,10) = 0.977 => 1.000 - 0.977 = 0.023
The probability of extracting more than 120 mg of caffeine from 8 fluid ounces of coffee brewed in a drip machine is 2.3%
