Exercise 1 Page 640

We have been given a normal distribution with mean $\mu$ and standard deviation $\sigma .$ We will find the probability that a randomly selected $x\text{-}$value from that distribution is less than $\mu -3\sigma .$ To find this probability, we will highlight the percent of data which is less than $3$ standard deviations below the mean.

Therefore, the probability that a randomly selected $x\text{-}$value from the distribution is less than $\mu -3\sigma$ equals $0.15\%,$ which can be also written as $0.0015.$