If X is normally distributed with mean 12 and standard deviation 4, then standard normal variable Z corresponding to X = 18 is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1.5
The standard normal variable is
\( \displaystyle Z = \frac{X-\mu}{\sigma} \)
\( \displaystyle Z = \frac{18-12}{4} = \frac{6}{4} = 1.5 \)
Z is positive because 18 is above the mean.