Question

Heather and her lab partners were trying to find the probability that the weight of a US quarter is below one standard deviation from the mean. They know that the weight of a quarter follows the normal distribution. What was their answer?

Answer 1

16%

Explanation:

The Empirical rule says that 68% of a normal distribution lies between -1 and +1 standard deviations.

That means that 32% lies outside of ±1 standard deviations.

Since the normal curve is symmetrical, that means 16% is less than -1 standard deviation and 16% is greater than +1 standard deviation.

So the answer is 16%.