Chapter 4.1, Problem 13P

Veterinary Science: Shetland Ponies How much should a healthy Shetland pony weigh? Let x be the age of the pony (in months), and let y be the average weight of the pony (in kilograms). The following information is based on data taken from The Merck Veterinary Manual (a reference used in most veterinary colleges).

x	3	6	12	18	24
y	60	95	140	170	185

(a) Make a scatter diagram and draw the line you think best fits the data.

(b) Would you say the correlation is low, moderate, or strong? positive or negative?

(c) Use a calculator to verify that $\sum x=63,\sum x^2=1089,\sum y=650,$ $\sum y^2=95,350,\text{and }\sum xy=9930.$ Compute r. As x increases from 3 to 24 months, does the value of r imply that y should tend to increase or decrease? Explain.