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This is an interactive plot for showing educational data for all 50 US states. In the initial scatterplot, we have the class size (students per teacher) on the x-axis and average composite SAT score on the y-axis. Color indicates the percent of students who take the SAT.
From this plot, there does not appear to be evidence of a direct linear relationship between class size and SAT performance. However, we can see a link between the number of students taking the SAT and the average performance in the state. States with few students taking the SAT (blue dots) tend to have better SAT scores, presumably due to self-selection (only the students who expect to do well will take the SAT).
By changing the Y-axis and color variables, we can also perform this test for the ACT, rather than SAT. Interestingly, here we do not seem to see the relationship between percent taking the test and performance.
There are a number of different variables which we can use; by selecting Latitude and Longitude for Y and X, we can produce a map. In this case, we see which states tend to use the SAT (yellow) and which tend to use the ACT (blue). The East Coast and West Coast states tend to use SAT, while those in the middle tend to use ACT.
In addition to selecting different variables for x axis, y axis, and color, we can also add some visual elements to the plot. For example, we can add the average class size and average composite SAT score to our earlier graph by clicking the "Show National Average" checkbox.
We can also add a visual color scale by checking the "Show Color Scale" checkbox.
Finally, to get the numbers for a specific state, we simply click on that state's point. Here, we can see that California only has 49% of students taking the SAT, and 15% taking the ACT.
There are certainly other interesting patterns to find in the data--please play around with it and see what you can find. This project was inspired by this FlowingData post; the data is for the 2006-2007 academic year (csv here, original SAT/expenditure/class size data from the National Center for Education Statistics, here and here; ACT data from act.org. Latitude and longitude from maxmind). The plot was built using flot, a javascript plotting library for jQuery.