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):
a. Does it appear that x and y are highly correlated?
b. The paper reported that r = .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 = 1) would result in this line. Do you agree? Explain your reasoning.

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