=+4. The article “Characterization of Highway Runoff in Austin, Texas, Area” (J. of Envir. Engr., 1998:

131–137) gave a scatterplot, along with the least squares line, of x 5 rainfall volume (m3

) and y 5 runoff volume (m3

) for a particular location. The accompanying values were read from the plot:

x: 5 12 14 17 23 30 40 47 y: 4 10 13 15 15 25 27 46 x: 55 67 72 81 96 112 127 y: 38 46 53 70 82 99 100