Import the data from data set corrExerciseB.
(a) Find the correlation between X and Y.
(b) Note that observations are put into one of four groups: A, B, C, and D. Find the mean of X and the mean of Y for each group.
(c) Create a scatter plot of the means (X A, YA), (XB, YB), ... and then find the correlation between the X¯ s, and the Y¯ s. Compare to (a). Ecological Correlation Correlations based on rates or groups are often higher than correlations based on individuals. This is a common problem in the social/behavior sciences where many data sets are based on summaries (e.g., census data for the 50 states: mean income levels, mean literacy rate, etc.).