Education Technology

# Knowledge Base

## Solution 11778: Different Logistic Regression Models Available On Current Texas Instruments Graphing Calculators.

### Why is the logistic regression computed on the TI-83 family, TI-84 Plus family, TI-Nspire family, and TI-Nspire handheld in TI-84 Plus mode different from the one computed on the TI-89 family, TI-92 family, and Voyage 200?

The logistic regression routines on the TI-83 family, TI-84 Plus family, TI-Nspire family, and TI-Nspire handheld in TI-84 Plus mode are different from the one computed on the TI-89 family, TI-92 family and Voyage 200.

The TI-83 family, TI-84 Plus, TI-Nspire family, and TI-Nspire handheld in TI-84 Plus mode fit the curve to the equation:

Y=c/(1 + a*exp (-b*x)).

The TI-89 family, TI-92 family and Voyage 200 fit the curve to the more general equation:

Y = a/(1 + b*exp (-c*x)) + d.

This therefore will return a different answer than the TI-83 family, TI-84 Plus family, TI-Nspire family, and TI-Nspire handheld in TI-84 Plus mode.

A free Statistics with List Editor calculator software application (App) for the TI-89 family, TI-92 Plus, and Voyage 200 contains the function "logist83", which duplicates the behavior of the TI-83 family, TI-84 Plus family and TI-Nspire handheld in TI-84 Plus mode.

The TI-Nspire family also has an additional command of LogisticD which will duplicate the regression available on the TI-89 family, TI-92 family, and Voyage 200.

For more information regarding your Texas Instruments graphing calculator, please refer to the guidebooks section.  If you have a TI-Nspire CX, TI-Nspire CX CAS, TI-Nspire or TI-Nspire CAS, please see the guidebooks for additional information.

Please Note: Users using a TI-Nspire in TI-84 Plus mode may refer to the TI-84 Plus guidebook.