Question

The ages of rocks in an isolated area are known to be approximately normally distributed with a mean of 7 years and a standard deviation of 1.8 years. Using the normalcdf function on your graphing calculator, what percent of rocks are between 5.8 and 7.3 years old?

Answer 1

The answer is B: 31.4%

Using a graphic calculator you have:

Mean: 7

SD: 18

Lower bound: 5.8

Upper bound: 7.3