This table gives a probability that a statistic is Gives a probability that a statistic is between 0 (mean) and Z. Since this is the portion of the area above Z, the proportion that is greater than Z isįound by subtracting Z from 1. This equates to the area of the distribution above Z.Įxample: Find Prob(Z ≥ 0.69). Gives a probability that a statistic is greater than Z. This value is found directly from the table. This equates to the area of the distribution below Z. Gives a probability that a statistic is less than Z. Z tables use at least three different conventions: Yield a probability of 0.25490 for a cumulative from mean table or 0.7549 from a cumulative table. These probabilities are calculations of the area under the normalĮxample: To find 0.69, one would look down the rows to find 0.6 and then across the columns to 0.09 which would The values within the table are the probabilities.The label for columns contains the least significant digits of Z.The label for rows contains the first two most significant digits of Z.If X is a random variable from a normal distribution with mean μ and standard deviation σ, its Z-score may beĬalculated from X by subtracting μ and dividing by σ.įor the average of a sample from a population in which the mean is μ and the standard deviation is σ, the standard Standard normal distribution, represented by the letter Z, is the normal distribution having a mean of 0 and a Normal distributions are symmetrical, bell-shaped distributions that are useful in describing real-world data. Then use the standard normal table to find probabilities. Since probability tables cannot be printed for every normal distribution, as thereĪre an infinite variety of normal distributions, it is common practice to convert a normal to a standard normal and Probability that a statistic is observed below, above, or between values on the standard normal distribution, and byĮxtension, any normal distribution. Which are the values of the cumulative distribution function of the normal distribution. A standard normal table, also called the unit normal table or Z table, is a mathematical table for the values of Φ,