My calculator displays an error message, "ERr: Invalid DIM" when I try to run a LinRegTTest. X and Y are using the right lines of data, L1 and L2.

Help lost my L1 or L2 on the Ti graphing calculator

Your TI-84 Plus displays the ERR:DIM MISMATCH error if you are trying to perform an operation that references one or more lists or matrices whose dimensions do not match.
For example, multiplying L1*L2, where L1={1,2,3,4,5} and L2={1,2} produces an ERR:DIM MISMATCH error because the number of elements in L1 and L2 do not match

Your assumption
--Next, I should be able to press VARS, move to Y-VARS, select FUNCTION, then select Y-1 and automatically enter the equation into Y-1.-
is not correct.

When you press [STAT[>][CALC][4:LinReg(ax+b)] or any other regression model,the command echoes on the main screen. If you press [ENTER] at this point, the calculator uses by default lists L1 and L2 and displays the resulting equation without copying it in a Y-variable.

If you want to have the equation copied on a Y-function, you should modify the command as follows
LineReg(ax+b) [SHIFT][1: L1] [,] SHIFT[2:L2] [,] [VARS][>:Y-Vars] [1:Function][1:Y-1][ENTER].

Here, [>] stands for RightArrow. For any other regression model, use the appropriate command.
At this point, the command line should look like the following:

LinReg(ax+b) L1, L2, Y1

Press [ENTER] to calculate you get the same screen as when you do not save the equation in Y1, but if you go to the Y= editor or press GRAPH, you will see the regression line superposed on the scatter plot.

what is the data you are inputting? try to make sure they're aren't any symbols

When you select 1-Var Stats, specify L2. If you don't specify a list, the calculator will assume L1.

You can recreate L1 by pressing
2ND [{] 1 STO 2ND [L1]

{ is on the ( key.
L1 is on the 1 key.

Hi vanman21,

You may have a plot on, other than the one your trying to use or, graph. You can press, [2nd] [Y=] and, [Arrow Up] to go to the plots and, make sure all other plots are off. As k_akima stated, your number of list elements may be wrong. You can display L1 and, L2 at the home screen or, in the plots menu and, make sure both list have the same length and, data is correct.

It is important to select L1 and L2 from the [2nd] [1] for L1 and, [2nd][2] for L2 on the calculator. If you type [alpha][L][1] won't work.

Next, press [STAT] [5]:SetUpEditor and, the SetUpEditor command will display at the Home screen for you. It is important to do this process before you start creating lists to be analyzed and, used on the calculator. This will save you a lot of hardships from data that is already being used and, in the calculator registers. You can also associate your list to your project so, that other data won't conflict and, cause errors.

You also should add the rest of the lists or, structure of the CubicReg(L1,L2,Frequency list,RegEQ). The SetUpEditor is a great tool to help you gain the proper structure. The default for frequency is sat at 1 if not used but, having a RegEQ (such as Y1), will help the calculator to calculate your data. Just remember to set the mode to Func before you use the SetUpEditor.

If you have any questions, just post a comment and, I'll respond quickly.

This means that the two lists containing your data do not contain the same number of points. If the data are not in L1 and L2, make sure you specify the two lists involved to the regression command.

If you have a frequency list it must be entered in a statistical list, L2, L3, ...or L6.
If the frequency of all elements is 1 you do not need to enter the frequency in a list. When you go to draw the box plot, the frequency will be set to 1.

1. Press [STAT][5:SetUpEditor][ENTER].
2. Press [STAT][1:Edit..]
3. Enter your data in L1.
4. Press [STAT][CALC][1:1-Var Stats].
5. Command echoes on main screen.
6. If ONLY one list contains data, it must be L1.
7. When you do not specify the list in the command line it will take L1 by default.
8. If L1 is empty and the data is in L2, or another but L1, the name of list must be specified.
   

Check the values you entered into L1 and L2. One of them is missing a value.