Question

If a sample of 10 cups of ice cream is selected, what is the probability that the mean of the sample will be larger than 670 mg? 

Answer 1

The average number of milligrams (mg) of cholesterol in a cup of certain brand of ice cream is 660 mg, and the standard deviation is 35 mg. assume the variable is normally distributed.

If a sample of 10 cups of ice cream is selected, what is the probability that the mean of the sample will be larger than 670 mg

Solution:

Given $\mu=660\ mg, \sigma=35\ mg, n=10$

$$P(X>670)=1-P(X\leq670)$$ $$=1-P(Z\leq\dfrac{670-660}{35/\sqrt{10}})$$ $$\approx1-P(Z\leq0.9035)\approx0.1831$$

The probability that the mean of the sample will be larger than 670 mg is 0.1831.