00stat3


 * Classpad 330 CAS Calculator ** toc


 * Statistics **

**A Scatter Plot**
Go to the Statistics Screen by clicking on Statistics icon in the main menu.

You will see a screen a bit like a spreadsheet with the rows numbered down the left side.

Enter your x values in the first blank column (LIST 1) (one value per line) Enter your y values in the corresponding row of the second blank column (LIST 2)

The screen shot to the right shows the Statistics screen with some data entered.

Drawing a Scatter Plot
Open the SETGRAPH menu.

The first box should be ticked (StatGraph1) Click on SETTING and you should see a pop up box like the one on the right.

Change the settings to
 * Draw** should be on[[image:00stat3b.gif width="265" height="246" align="right"]]
 * Type**: Use the dropdown menu to select **Scatter**
 * XList** = List 1
 * YList** = List 2
 * Freq** = 1

{Experiment with the type of Mark for each data point to find one you like}

Click SET and you will be returned to the Statistics screen.

Now click the graph icon (first one on the left)

The calculator screen will now split into two and display a scatter plot in the bottom half of the screen. Only one of the two split screens can be active. You can jump between the two screens by clicking anywere in the other screen, or by clicking on the first icon on the left (which now looks like a table.)

The icon bar and the menu bar change depending on which screen is active.

The **Resize** and **Swap** icons in the green bar at the bottom of your screen allow you to change the position of the two split screens.

You may need to adjust the scale on the x-axis (xmin and xmax) and the scale on the y-axis (ymin and ymax) so that your data is properly displayed within the screen.

The XY icon allows you to step through the columns using the blue arrow keys on your keypad and view the data for each column. This icon only appears when the graph screen is active.

Linear Regression
(or Line of Best Fit) With either the table screen or the graph screen active, go to the CALC menu and select Linear Regression.

You should see a pop-up box like the one shown on the right.

Use the drop down menus to set:
 * XList** = list 1
 * YList** = list 2
 * Freq** = 1

If you wish to, you can set Copy Formula = Y1. This will place a copy of the equation produced by linear regression into the graphing section of the calculator.

Press OK and you will see a screen like this:

The equation of the line of best fit is provided in the format: y = ax + b with a = 2.93 and b = –0.30.

This means the equation is: y = 2.93x – 0.30

R-Squared Correlation
The r 2 value is a measure of how closely the data fits to the line (correlation). An r 2 value of 1.0 means all the data is exactly on the line. r 2 values greater than 0.9 indicates a strong correlation. (the data is close to being in a straight line).

[[image:00stat3linregc.gif width="260" height="142" align="right"]] Line of Best Fit
Press OK and the calculator will draw in the Line of Best Fit as produced by the linear regression process above.

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