=+5.11 The accompanying scatterplot shows observations on hemoglobin level, determined both by the standard spectrophotometric method (y) and by a new, simpler method based on a color scale (x) (“A Simple and Reliable Method for Estimating Hemoglobin,” Bulletin of the World Health Organization [1995]: 369–373):

2 4

6 8

10 12 14 16 2 4 New method (g/dl)

6 8 10 12 14