How do you find the equation of a regression line with a TI-83?
Enter the data into two lists first.
I will use brackets to indicate a button on the calculator and ALL CAPS to indicate what function to use.
Let X and Y be your two variables, corresponding to a collection of points.
Press [STAT] and then choose EDIT or press [ENTER].
This will open up the lists where you will enter the data.
Enter all of the values for X in list 1, one by one. Put a value in, then press [ENTER] to move down to the next line.
Now enter all of the values for Y into list 2 the same way.
Now press [STAT] again.
Use arrow keys to move to the CALC list of functions.
These are statistical calculations.
Choose item , which is labeled LinReg(ax + b).
That is, this is the Linear Regression function of the TI-83.
On the next screen, type
[2nd]  [,] [2nd] .
Notice that you need the comma button.
This tells the calculator which lists you will be using for regression. [2nd]  means List 1, for example.
Then press [ENTER], and voila!