The paper “Crop Improvement for Tropical and Subtropical Australia: Designing Plants for Difficult Climates” (Field Crops Research [1991]: 113–139) gave the following data on x = crop duration (in days) for soybeans and y = crop yield (in tons per hectare):

a. Construct a scatterplot of the data. Do you think the least-squares line will give accurate predictions? Explain.

b. Delete the observation with the largest x value from the sample and recalculate the equation of the least-squares line. Does this observation greatly affect the equation of the line?

c. What effect does the deletion in Part (b) have on the value of r²? Can you explain why this is so?

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X y x y 92 1.7 102 1.7 Σ x = 1060 92 2.3 96 1.9 106 106 1.6 1.8 Σ y = 15.8 a = 5.20683380 100 2.0 121 1.0 102 1.5 143 0.3 Σ xy = 1601.1 b = -0.3421541