Question: A study on the relation between rejection and depression in adolescents conducted by one of the authors (Nolan, Flynn, & Garber, 2003) also collected data on externalizing behaviors (e.g., acting out in negative ways, such as causing fights) and anxiety. We wondered whether externalizing behaviors were related to feelings of anxiety. Some of the data are presented in the accompanying table.
a. Create a scatterplot of these data. Be sure to label both axes.
b. What does the scatterplot suggest about the relation between these two variables?
c. Would it be appropriate to calculate a Pearson correlation coefficient? Explain your answer.
d. Construct a second scatterplot, but this time add in the data for one more participant who scored 1 on externalizing and 45 on anxiety. Would you expect the correlation coefficient to be positive or negative now? Small in magnitude or large in magnitude?
e. The Pearson correlation coefficient for the first set of data is 0.65; for the second set of data it is 0.12.
Explain why the correlation changed so much with the addition of just one participant.