The following table gives the number of organ transplants performed in the United States each year from 1990 to 1999 (The Organ Procurement and Transplantation Network, 2003):

Year Number of Transplants (in thousands)
1 (1990) 15.0 2 15.7 3 16.1 4 17.6 5 18.3 6 19.4 7 20.0 8 20.3 9 21.4 10 (1999) 21.8

a. Construct a scatterplot of these data, and then find the equation of the least-squares regression line that describes the relationship between y  number of transplants performed and x  year. Describe how the number of transplants performed has changed over time from 1990 to 1999.

b. Compute the 10 residuals, and construct a residual plot. Are there any features of the residual plot that indicate that the relationship between year and number of transplants performed would be better described by a curve rather than a line? Explain.