1. Using a sample of 120 high schools, a researcher obtains a correlation of r = -.52 (p < .05) between average teacher salary (X) and the proportion of students who drop out (Y). Considering the earlier discussion of correlation and causation (Section 7.6), what do you believe is the most likely explanation of why these two variables correlate?
2. A researcher believes that the ability to identify constellations of stars in the night sky is related to spatial reasoning ability. She obtains the correlation between scores on a spatial reasoning test (X) and the number of constellations correctly identified (Y). She calculates this correlation for each of two samples: one is based on a random sample of adults in her community, and the other is drawn from members of a local astronomy club. Which correlation would you expect to be larger? (Explain.)