<P> A standard normal table, also called the unit normal table or Z table, is a mathematical table for the values of Φ, which are the values of the cumulative distribution function of the normal distribution . It is used to find the probability that a statistic is observed below, above, or between values on the standard normal distribution, and by extension, any normal distribution . Since probability tables cannot be printed for every normal distribution, as there are an infinite variety of normal distributions, it is common practice to convert a normal to a standard normal and then use the standard normal table to find probabilities . </P> <P> Normal distributions are symmetrical, bell - shaped distributions that are useful in describing real - world data . The standard normal distribution, represented by the letter Z, is the normal distribution having a mean of 0 and a standard deviation of 1 . </P> <P> If X is a random variable from a normal distribution with mean μ and standard deviation σ, its Z - score may be calculated from X by subtracting μ and dividing by the standard error: </P> <Dl> <Dd> Z = X − μ σ (\ displaystyle Z = (\ frac (X - \ mu) (\ sigma))) </Dd> </Dl>

Standard normal distribution table area to the left of z