Errors that occur when graphing equations:
There are several common errors that will cause the graphing calculator to give an error message and not allow students to graph an equation. Here are some of the most common ones.
- "Plots" are turned on. Above the place where equations are entered are the tabs that turn on "stat plots" which are used to graph data from a table. If the table is blank, and it usually is, the calculator will give an error message if the "Plots" are accidentally selected.
- Use of minus button instead of negative button. On paper we draw these the same but the calculator will not graph if the first symbol is a minus sign when it is supposed to be a negative sign (found on last row of keys next to "Enter" AKA "equal").
- "Window Error" occurs when the a minimum value for the graphing window is larger than the maximum value or the two values are the same. The easiest way to fix this is to go to "Zoom" and select "6:Standard." This creates a 10 unit window in all directions. Also is the best way to start all graphs.
- It graphs but no graph is visible, just a blank screen. Start with standard zoom then if nothing is visible go to "Zoom" and "Zoom out." This is not the only solution but may help. You should also check the window and look at the table of values (another thing the calculator does for you).
- The graph doesn't look like what you expected. A common cause can be a lack of parentheses. The safest fix is to put numerators and denominators in parentheses even if the equation on paper did not have it. Generally, graphing calculators need more parentheses than one might expect since equations are written out in a single line. This looks different than how we write on paper.
Errors that occur with stat plots and regression equations:
- You don't know where to start: most steps have you start by hitting the "stat" button.
- Your table has numbers in it already: always start each new problem by clearing the list.
- Your scatter plot does not show up on graph: check the window and see if your actual data fits inside it, check that you have turned on "plot" from equation (or "stat plot" window.
- No r value given when calculating your regression equation: go to "mode" (uses shift then mode), and turn on "stat diagnostics." Then rerun your linreg calculation.
- How do I calculate the linear regression equation? Hit "stat", scroll right to "calc," select "linreg (ax+b)" and hit enter a few times. Make sure the correct lists are selected.
Photo used under Creative Commons from Austin Community College