equation defining normal distribution
The normal distribution is defined by the following equation: Normal equation. The value of the random variable Y is: where X is a normal random variable, Î¼ is the mean, Ï is the standard deviation, Ï is approximately 3.14159, and e is approximately 2.71828.Y = { 1/[ Ï * sqrt(2Ï) ] } * e. The random variable X in the normal equation is called the normal random variable.e enter these values into the Normal Distribution Calculator and compute the cumulative probability. The answer is: P(X. 365) = 0.90. Hence, there is a 90% chance that a light bulb will burn out within 365 days. Example 2. Suppose scores on an IQ test are normally distributed.