These areas are thus the probability that z will be less than or equal to that value. The z table gives the area under the standard normal distribution to the left of different z values. Since the standard normal probability distribution is a continuous probability distribution, probabilities are given by the area under the graph. Furthermore, the distribution is symmetric about the mean, with the right side of the curve being a mirror image of the left side. The mean of the distribution is in the middle, which is also the highest point on the curve. Like the normal probability distribution, the standard normal probability distribution has a bell-shape. The standard normal probability distribution is simply a normal probability distribution with a mean of zero and a standard deviation of one.

The standard normal table, or z table, provides probabilities for the standard normal probability distribution.