Click on the question to jump to the answer. Also consult the TI-86 tutorial for detailed instructions on operating the TI-86.
Q1. The display is getting dim. Do I need new batteries?
Q2. Will I lose all the programs if I change the batteries?
Q3. Why won't my function graph?
Q4. Why won't my data plot?
Q5. What does "Error 12 Dim Mismatch" mean?
Q6. How do I get my regression (best fit) function
into y1?
Q7. When I try to run one of the programs, I keep
getting "Error 10 Data Type". How do I fix this?
Q8. There's no y1 in my y(x) list. How do I get it back?
Q9. I entered an equation into the Solver, and one
of the variables in my equation is not on the list of variables. How
do I fix this?
Q10. I'm trying to graph a function, but I keep
getting "Error 13 Dimension". What does this mean?
Q11. How do I get rid of the menus if they are
obscuring part of my graph?
Q12. I graphed my regression (best fit) function on
top of my data. How come I can't trace along the function?
Q13. The names of my lists (2nd STAT EDIT or 2nd
LIST EDIT) are goofed up. How do I fix this?
Q1. The display is getting dim. Do I need new batteries?
Try adjusting the contrast first. Press 2nd and then the up arrow to make the display darker. (Press 2nd and then the down arrow if you overshoot and need to make it lighter). As you do this, notice the number that appears in the upper right corner of the screen. This number indicates the contrast level, on a scale of 1 to 9. If you have to set it to 8 or 9 to see the display clearly, you will need to change the batteries soon; if you don't need to set it that high, your batteries are fine. If the batteries ever do get very low, you may get a "low batteries" message when you turn the calculator on, alerting you to change them as soon as possible. You should also change the backup battery every few years.
Q2. Will I lose all the programs if I change the batteries?
As long as the calculator is turned off and the backup battery is working, you should not lose anything when you change the four AAA batteries. If the calculator is on when the batteries are removed (for example, if you drop the calculator while using it and the batteries fall out), or if the backup battery is more than a few years old, you will probably lose programs and whatever else you have stored. If this happens, ask your instructor to copy the programs back onto your calculator.
Q3. Why won't my function graph?
Make sure that you entered your function using a lower case x for the variable (use the x-VAR button, or get "x" off the menu), and check that your function is turned on. "SELCT" (F5 on the y(x) menu) selects or deselects functions, i.e., turns them on or off. A function is on if there is a dark box around the equal sign, otherwise it is off. If the function is turned on but you still cannot see the graph, check your window settings--it may be that the function did graph, but it is completely outside the window you have set.
Make sure that your data is entered correctly in the lists xStat, yStat. Go to GRAPH, then "y(x)=", and check that Plot1 is turned on (it is on if there is a dark box around the name "Plot1" at the top of the screen); if it is not, put the cursor on "Plot1" and use "SELCT" to turn it on. Make sure that your window is set appropriately for your data. If the plot still will not display, or if you are getting a strange type of plot instead of the usual scatter plot, check the plot settings.
Q5. What does "Error 12 Dim Mismatch" mean?
This means that your lists, xStat, yStat, and fStat, are not all the same dimension (length). Check to see that your data is entered correctly in xStat and yStat. Use the DEL key or 2nd INS if you need to delete or insert entries. The list fStat needs to be the same length as xStat and yStat, with each fStat entry equal to 1. You can enter the ones into fStat yourself, or exit and run the program "ONES" to do this automatically.
Q6. How do I get my regression (best fit) function into y1?
A6. When you compute the regression function (from the STAT CALC menu), simply type in y1 (use 2nd alpha to get the lower case y) immediately after selecting the type of regression, before you press Enter. For example, if you are computing a logistic regression, it would look like this:
LgstR y1
When you press Enter, the calculator will compute the logistic function (or whatever function you select) that best fits your data and paste the function into y1. If you go to GRAPH, then "y(x)=", your best fit function should be in y1; when you display the graph, it will be graphed along with the scatter plot of the data (assuming you left Plot1 turned on).
Q7. When I try to run one of the programs, I keep getting "Error 10 Data Type". How do I fix this?
You probably stored a picture or graph data base to a variable name that conflicts with a variable name used by the program. Here's how to fix it (ask your instructor if you need help with this). Go to the memory management screen [2nd MEM], select "DELET" "ALL", scroll down the list of variables and see if you have one that says GDB (graph data base) or PIC (picture). If you find one, and it's not something you want to keep, simply delete it (pressing ENTER deletes whichever variable the cursor is on; be careful not to delete things you need, such as programs). If the PIC or GDB is something you do want to save, go to GRAPH, then "RCPIC" (recall picture) or "RCGDB" (recall graph data base) and type in the name of your picture or graph data base (and ENTER), then store it (STPIC or STGDB) with a new name; then go back to [2nd MEM] and delete the original one. This should correct the problem.
Q8. There's no y1 in my y(x) list. How do I get it back?
When you call up the y(x) list, the list starts with the first y variable in which you have a function stored; if there are no functions in any of the y-variables, it will start with y1. If your first function is in, say, y3, the list will start at y3. Use "INSf" (insert function) from the menu to insert y2 and y1 (or whatever). Alternatively, you can clear whatever function(s) you have stored, exit, and come back--the list will then start with y1.
Q9. I entered an equation into the Solver, and one of the variables in my equation is not on the list of variables. How do I fix this?
This can happen if one of the variables used in your equation was already defined as an equation. For example, if you had previously defined Y=R^2, and then used the variable Y in some other equation in the Solver, then R will appear in the list of variables, but Y will not. To fix this, exit to the homescreen and clear the missing variable (in this example Y) by storing a zero to it (type 0 then press the store button then Y then Enter).
Q10. I'm trying to graph a function, but I keep getting "Error 13 Dimension". What does this mean?
This most likely means that you left Plot1 turned on, with no data entered in xStat, yStat. Go to GRAPH, "y(x)=", and turn off Plot1 (put the cursor on Plot1, and press "SELCT" (F5) to turn it off). Your graph should now display. (Plot1 is on if there is a dark box around it, otherwise it is off.)
Q11. How do I get rid of the menus if they are obscuring part of my graph?
Press the CLEAR button to get rid of the menus, and EXIT to get them back.
If Plot1 is turned on, when you press TRACE, it will initially say "P1" in the upper right corner of the screen. This means you are tracing along Plot1 (your scatter plot). To trace along the function that you have in y1 (or y2 or wherever), simply press the down arrow to get to the function that you want (y1 is indicated by a "1" in the upper right of the screen, y2 by a "2", etc.); you can then trace along your function.
Q13. The names of my lists (2nd STAT "EDIT" or 2nd LIST "EDIT") are goofed up. How do I fix this?
Exit out of the list editor. Then press 2nd LIST "OPS" MORE MORE MORE "SetLE" ENTER. This will reset the list editor, so that the lists xStat, yStat, and fStat appear in the usual places. (You will probably need to re-enter your data.)
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