The Normal Distribution is also called the Gaussian distribution. It is defined by two parameters mean ('average' m) and standard deviation (σ). A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve symmetrical about the mean.
m = Mean. σ = Standard Deviation. X = Normal Random Variable
If X is a normal random variable with mean (m) 100 and standard deviation (σ) 6 find P(X<106)
For a given value X=106 Z = (106-100)/6 = 1
Find the value of 1 in Z table Z = 1 = 0.3413
Here the X value is greater than mean P(X) = 0.5 + 0.3413 = 0.8413