Question: what is the formula for standard normal?
Answer: The following formula converts an X value into a Z score, also called a standardized score: where μ is the mean and σ is the standard deviation of the variable X. In order to compute P(X < 30) we convert the X=30 to its corresponding Z score (this is called standardizing): Thus, P(X < 30) = P(Z < 0.17).