In many reallife situations, scatter plots follow patterns that are approximately linear. If y tends to increase as x increases, then the paired data are said to be a positive correlation. If y tends to decrease as x increases, the paired data are said to be a negative correlation. If the points show no linear pattern, the paired data are said to have relatively no correlation. 

Setting up a scatter plot
Example: Is there a relationship between the fat grams and the total calories
in fast food? (refer to the data below)
Sandwich 
Total Fat (g) 
Total Calories 
Hamburger 
9 
260 
Cheeseburger 
13 
320 
Quarter Pounder 
21 
420 
Quarter Pounder with Cheese 
30 
530 
Big Mac 
31 
560 
Arch Sandwich Special 
31 
550 
Arch Special with Bacon 
34 
590 
Crispy Chicken 
25 
500 
Fish Fillet 
28 
560 
Grilled Chicken 
20 
440 
Grilled Chicken Light 
5 
300 

1. Enter the Fat grams into column A of the spreadsheet. Label the column "fat". Enter the Calories into column B and label the column "cal". Be sure you have the same number of entries in both columns.
(See Lists and Spreadsheets for entering data in lists.)

Once the data is entered, there are two ways to obtain a scatter plot.
METHOD 1: (Data & Statistics)
2. Graph the scatter plot. From HOME, choose #5 Data and Statistics. Hit ENTER.
Using the Nav Pad, arrow to the bottom of the screen and choose the xvariable to be "fat". Then move to the left side of the screen and choose the yvariable to be "cal". You will now see your scatter plot.


METHOD 2: (Graphs & Geometry)
2. From HOME, choose #2 Graphs&Geometry. From MENU, choose #3 Graph Type and #4 Scatter Plot, as seen at the right.
Hit ENTER.
3. At the bottom of the screen, highlight the box naming the set to be used for the xvalues, click, and choose "fat". Use your TAB key to highlight box if needed. Do the same for the y set and choose "cal". 




4. From MENU, choose #4 Window and #9 Zoom Data, to set the window for the plot.
Hit ENTER. 




In both methods, visual examination shows a positive correlation between the total grams of fat and the total calories. (The graph resembles a straight line rising to the right.)
Let's move on to "line of best fit" and see how the calculator can find the best equation to represent this data. 