TI-83 Instructions

Computing a Standard Normal Probability

Z is the standard normal random variable.

The three basic forms are:

• P(Z < a)
• P(Z > a)
• P(a < Z < b)

Standard Normal Probability P(Z < a)

1. Press 2nd DISTR. The DISTR menu title is highlighted.
2. Select normalcdf, item #2, or press 2 and skip the next step.
3. Press ENTER. The phrase normalcdf( appears in the display.
4. Enter -5 (or any negative number beyond -5).
5. Press comma.
6. Enter the value of a.
7. Press ).
8. Press ENTER. The value of P(Z < a) appears.

Standard Normal Probability P(Z > a)

1. Compute P(Z < a) according to the above instructions.
2. Subtract the value of P(Z < a) from 1. The result is P(Z > a).

Standard Normal Probability P(a < Z < b)

1. Compute P(Z < a) according to the above instructions.
2. Compute P(Z < b) according to the above instructions.
3. Subtract the value of P(Z < a) from P(Z < b). The result is P(a < Z < b).