emerpical rule

Question

Suppose that the mean height of 10th grade boys is 69 inches with a standard deviation of 2 inches and that it follows a normal distribution. Using the empirical rule, determine the percentage of 10th grade boys below 67 inches.

Answer 1

There are a few things you need to know to solve this problem  

 

First, the empirical rule states (in part) that in a normal distribution 68% of the data will be within one standard deviation of the mean  

 

Second, a normal distribution is symmetric about the mean

 

Finally, note that 67 = 69 - 2 is one standard deviation below the mean  

 

Can you figure out the answer to the question using this information?