Suppose That the Distribution of Heart Rates for Medium-Sized Dogs

Multiple Choice

Suppose that the distribution of heart rates for medium-sized dogs is Normally distributed with mean 115 beats per minute and standard deviation 18 beats per minute.
Approximately what percentage of medium-sized dogs have a heart rate below 115 beats per minute?

A) 16%
B) 34%
C) 50%
D) 68%
E) 95%