2.56 Use the applet. Go to the Correlation and Regression applet. Click on the scatterplot to create a group of 12 points in the lower-right corner of the scatterplot with a strong straight-line negative pattern (correlation about −0.9).

1. (a) Add one point at the upper left that is in line with the first 12. How does the correlation change?

2. (b) Drag this last point down until it is opposite the group of 12 points. How small can you make the correlation? Can you make the correlation positive? A single outlier can greatly strengthen or weaken a correlation. Always plot your data to check for outlying points.