Suppose we fit a least-squares regression line to a set of data. What is true if a plot of the residuals shows a curved pattern?
a. A straight line is not a good model for the data.
b. The correlation must be 0.
c. The correlation must be positive.
d. Outliers must be present.
e. The regression line might or might not be a good model for the data, depending on the extent of the curve.
Answer: a. A straight line is not a good model for the data.