Selenium (Se) is an essential element that has been shown to play an important role in protecting marine mammals against the toxic effects of mercury (Hg) and other metals. It has been suggested that metal concentrations in marine mammal teeth can potentially be used as bioindicators for body burden. Twenty Belugas (Delphinapterus leucas) were harvested from the Mackenzie Delta, Northwest Territories, in 1996 and 2002, as part of an annual traditional Inuit hunt. Tooth and liver Se concentra¬tions are reported in the table, summarized, and graphed.41

(a) Can we regard the sample correlation between Tooth (Y) and Liver (X) selenium, r = 0.53726, as an estimate of the population correlation coefficient? Briefly explain.
(b) If the circled point were removed from the data set, would the sample correlation listed in part (a) increase, decrease, or stay about the same?

(c) If the roles of X and Y were reversed (i.e., Y = Liver and X = Tooth selenium), would the sample correlation listed in part (a) increase, decrease, or stay about the same?
(d) Is the circled point on the plot a leverage and/or influential point? Explain briefly.
(e) Is the circled point on the plot an outlier?

Transcribed Image Text:

240 220 s 200 180 160- 40 120 10 20 30 Liver Se (ug/g dry wt) Liver Tooth Liver Tooth Se Se Whale (Ag/g) (ng/g) Whale (ug/g) (ng/g) 6.23 140.16 15.28 112.63 2 6.79 13332 18.68 245.07 7.92 135.34 13 22.08 140.48 4 8.02 12782 142755 177.93 5 9.34 0.67 15 32.83 160.73 10.00 146.22 16 36.04 227.60 7 10.57 3118 17 37.74 177.69 8 1104 45.51 8 40.00 174.23 9 12.36 163.24 9 123 206.30 10 1453 13655 20 4547 141.31