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?

16%

Step-by-step 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%.