CR5.15 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 Reference method (g/dl)

a. Does it appear that x and y are highly correlated?

b. The paper reported that r 5 .9366. How would you describe the relationship between the two variables?

c. The line pictured in the scatterplot has a slope of 1 and passes through (0, 0). If x and y were always identical, all points would lie exactly on this line. The authors of the paper claimed that perfect correlation (r 5 1) would result in this line. Do you agree? Explain your reasoning.