There are 3 instances in which you may be looking at z-values. 1) when z is positive, 2) when z is negative, and 3) when you will be looking at ranges between 2 values of z (which could be positive or negative) Below I outline these instances and the rules you will need to know to correctly use the z-table to calculate probabilities.

z = (x-μ)/σ

**1) If z is positive:**a) the probability of observing a lower value of z is the area to the left of z and is the value taken directly from the standard normal table.

b) The probability of a larger value of z is the area to the right of z and = 1-(value from the table)

**2) If Z is negative:**a) The probability of a lower z is the area to the left of z and = 1-(value from table)

b) The probability of a higher value of z is the area to the right of z and = the value directly from the table.

__is the area between -z and z. You get this by:__

**3) The probability of getting a value between -z and z**a) calculate the area < - Z= A

b) calculate the area > Z =B

c) calculate 1 - A -B