Solution 36295: Calculating A Normal Cumulative Distribution (normalcdf) on the TI-83 Plus Family of Graphing Calculators.
How do I calculate a Normal Cumulative Distribution (normal cdf) on the TI-83 Plus family of graphing calculators?
Use the following example as a guide when calculating for the normal CDF on the TI-83 Plus family of graphing calculators.
Lower Bound: 5
Upper Bound: 15
Standard Distribution: 2.5
1) Press [2nd] [VARS] [Down] [Enter]
2) Next to normalcdf( enter  [,]  [,]  [,] [2.5] [)]
3) Press [Enter] and it will display the answer
Please see the TI-83 Plus Family guidebooks for additional information.