The focal point of an agricultural research study was the relationship between the time a crop is planted and the amount of crop harvested. If a crop is planted too early or too late, farmers may fail to obtain optimal yield and hence not make a profit. An ideal date for planting is set by the researchers, and the farmers then record the number of days either before or after the designated date. In the following data set, D is the number of days from the ideal planting date and Y is the yield (in bushels per acre) of a wheat crop:

a. Plot the data in a scatterplot.
b. Describe the relationship between the number of days from the optimal planting date and the wheat yield.
c. Calculate the correlation coefficient between days from optimal planting and yield.
d. Explain why the correlation coefficient is relatively small for this data set.

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D -19 18 15 12 96-3-1 0 Y 30.7 29.7 448 414 481 428 49.946.9 46.4 53.5 D 1 Y 55.0 469 44 50.2 41.0 428 365 35.8 32.2 233 3 8 12 15 17 19224