LAB 6: Scatterplots:
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The Scatterplot displays the relationship between two interval level variables. By convention, the dependent variable is displayed on the Y-axis and the independent variable (the variable that is assumed to "cause" the other) is displayed on the X-axis.
The chart on the left (click on it for full image), contains two additional features: each state is represented by a label (rather than a dot) and linear regression line.
Standards for Scatterplots:
- The dependent variable is always on the Y-axis.
- The data points should take almost all of the plot area.
- Each variable should be labeled on the appropriate axis.
For this lab you can either use a state or country-level data with data on your topic, or, use this State education data set.
Instructions for creating a scatterplots:
- The Chart Wizard only works if the independent variable (the X axis variable) is on the left of the dependent variable. (if they are backwards, the X variable will be on the Y axis).
- Select both variables with the mouse, include the variable name at the top (enter these on the first row).
- Insert a chart, select a scatterplot, without lines.
- Format the chart.
- eliminate the background
- reset the minimum values on the x and y axis scales
- You can also add a trendline, select it from the chart menu.
- Use the J-Walk Chart Tools to label the data points:
- select the Chart, then from the menu choose Chart | J-Walk - data labels
- click on the select data label range
- go to the data sheet, select the state id codes and hit enter.
- format the data range -- eliminate the marker
- format the data labels -- center everything.
State Data for Term paper topics
Step 1. Find your dependent variable. Search for state data on your topic. Here's a suggested list of independent and dependent variables:
| Independent | Dependent |
| Severity of state gun laws | Murder rate, gun death rate |
| Number of executions since 1975 | % change in state murder rate from 1975 to 2001 |
| poverty rate | Infant mortality death rate |
| % of population (or children or women) uninsured |
Infant mortality death rate |
| % of the labor force unionized | Economic growth rates: (change in per capita
income, state GSP, value added by manufacturing..) |
| % of population in prison | Change in crime rates |
| school spending, class size, school size.... | state math or reading scores (state education data) |
Note, for some of your topics, country data or city data can also be used for this assignment.
One source of state data is the statistical abstract. To find the data browse the "state data" or "state and local government data" on the bookmarks of the file that loads when you first launch the abstract.
Step 2. Download this file -- which contains further instructions, a listing of the 50 states with the two-digit state ID code.
If you are using your computer at home (not in an ISU lab), you may download the J-Walk Chart Tools. It will add a menu item under "Chart" for labeling charts and copying chart images. Download the file to your disk and click on the program to install the tools in Excel.
To select other variables that are not adjacent to each other for other charts,
- Begin the chart wizard with just the dependent variable selected.
- On the second step of the chart wizard, select the X-series.
- Click on the box on the right and select just the data (not the label) from the variable range.