1. The problem asks to find the area $P(Z < -1)$ where $Z$ is a standard normal random variable. 2. For a standard normal distribution, $Z$ has mean 0 and standard deviation 1. 3. The area $P(Z < z)$ corresponds to the cumulative distribution function (CDF) value at $z$. 4. Using standard normal distribution tables or a calculator, find $P(Z < -1)$. 5. From the standard normal table, $P(Z < -1) = 0.1587$. 6. This means the probability that $Z$ is less than -1 is approximately 0.1587. Final answer: $P(Z < -1) = 0.1587$