# TI-82: Scatter Plots, Regression Lines

You can use the calculator to draw scatter plots.

See the instructions on using the calculator to
do statistics and lists. This provides an overview as well as some helpful
advice for working with statistics on the calculator.

## Scatter Plots

- Enter the
*x* values into L_{1} and the *y* variables
into L_{2}.
- Go to Stat Plot (2nd y=)
- Turn Plot 1 on
- Choose the type to be scatter plot (1st type)
- Set Xlist to L
_{1}
- Set Ylist to L
_{2}
- Set the Mark to any of the three choices
- Zoom to the Stat setting (#9)

Note, the Ylist and Mark won't show up until you select a scatter plot

## Regression Lines

- Setup the scatter plot as instructed above
- Go into the Stats, Calc, Setup screen
- Setup the 2-Var Stats so that: Xlist = L
_{1}, Ylist = L_{2},
Freq = 1
- Calculate the Linear Regression (ax+b) (#5)
- Go into the Plot screen.
- Position the cursor on the Y1 plot and hit CLEAR to erase it.
- While still in the Y1 data entry field, go to the VARS, STATS, EQ screen
and choose option 7 which is the regression equation
- Hit GRAPH

## Regression Lines, part 2

The above technique works, but it requires that you change the equation being
graphed every time you change problems. It is possible to stick the regression
equation "ax+b" into the Y1 plot and then it will automatically graph
the correct regression equation each time.

### Do this once

- Setup the scatter plot as instructed above
- Go into the Plot screen.
- Position the cursor on the Y1 plot and hit CLEAR to erase it.
- Enter
` a*x+b ` into the function. The a and b can be found under
the VARS, STATS, EQ screen

### Do this for each graph

- Go into the Stats, Calc, Setup screen
- Setup the 2-Var Stats so that: Xlist = L
_{1}, Ylist = L_{2},
Freq = 1
- Calculate the Linear Regression (ax+b) (#5)
- Hit the GRAPH key

It is important that you calculate the linear regression variables before
trying to graph the regression line. If you change the data in the lists or
have not calculated the linear regression equations, then you will get an "
ERR:
Undefined" when you try to graph the data.

Be sure to turn off the stats plots and/or the Y1 plot when you need to graph
other data.