# TI-83 Instructions

## The Regression Line and the Correlation Coefficient

### Computing the Equation of the Regression Line and the Correlation Coefficient

1. Enter the x values into List `L1`.
2. Enter the y values into List `L2`.
3. Press `STAT`.
4. Select the `CALC` menu title.
5. Select menu item #8, `LinReg(a + bx)`. (Menu item #4 is similar, but I prefer #8.)
6. Press `ENTER`. The phrase `LinReg(a + bx)` appears in the display.
7. Press `2nd L1`.
8. Enter a comma.
9. Press `2nd L2`.
10. Press `ENTER`. The display shows the equation `y=a+bx` as a reminder of what `a` and `b` stand for. It also shows the values of `a` and `b`. Note that `b` is the slope b1 and `a` is the y-intercept b0.
11. Below `a` and `b` are displayed `r2` and `r`.

### Graphing the Regression Line

1. Follow the above steps to compute the equation of the regression line. A consequence of this is that the coefficients will be stored in the calculator. (This step is necessary.)
2. Press `Y=` (in the upper left corner).
3. Select a function variable by moving the cursor to that line, say `Y1`.
4. Press `VARS`. Some menu titles appear. The `VARS` menu title is highlighted
5. Use the down arrow to select menu item #5, `Statistics...`
6. Press `ENTER`. The `Statistics` menu titles appear.
7. Select the `EQ` menu title.
8. Press `ENTER` to select menu item #1, `RegEQ`. This is the expression `a + bx` that was previously calculated. It is now pasted into the function `Y1`.
9. Create a scatter diagram. When the scatter diagram is drawn, the regression line will also be drawn.