>In my research methods course students have collected data so that they >can compute one simple correlation (n=180). Both questions are on >5-point scales. I want them to plot the data to see if it looks like >there is a correlation. However, a simple scatter plot is uninformative >because there is at least one subject who is reporting every combination >on the 2 questions (so the scatterplot looks like a grid). Is there some >way of plotting the data so that the "dots" are bigger when there are >many cases. Or maybe one needs an entirely different plotting strategy. >I use SPSS. Help? ========================= One creative solution I ran across is this: create a "jittered" scatterplot. Jittering simply moves dots to one side or the other, letting you see how many there are. It's sort of like stacking pennies in several piles on a table, then shaking or jittering the table and having the pennies scatter near their original spots. Here's how to do it in SPSS: Suppose you want to plot height vs. sex for N=100 males and females. Create a new variable using COMPUTE: sexj=rv.norm(sex,.1) [rv.norm is a function that can be picked off the function list--it randomly and normally distributes the points] now just do a scatterplot of height vs. sexj You'll be able to see the number of points near each combination. If you have two categorical variables, you could do the jittering in both directions if you wish.
Allen Shoemaker Calvin College --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
