19. How old is that tree? One can determine how old a tree is by counting its rings, but that requires either cutting the tree down or extracting a sample from the tree’s core.

Can we estimate the tree’s age simply from its diameter?

A forester measured 27 trees of the same species that had been cut down, and counted the rings to determine the ages of the trees.

a) Create a scatterplot and describe the trend you see.

b) Find the correlation.

c) How is the value of the correlation affected by the fact that the data are averages rather than percentages for each of the 50 states?

d) Write a linear model and interpret the slope in context.

Diameter (in.) Age (yr) Diameter (in.) Age (yr) 1.8 1.8 2.2 458 4 10.3 23 14.3 25 13.2 28 4.4 8 9.9 29 6.6 8 13.2 30 4.4 10 15.4 30 7.7 10 17.6 33 10.8 12 14.3 34 7.7 13 15.4 35 5.5 14 11.0 38 9.9 16 10.1 12.1 12.8 2822 15.4 38 18 16.5 40 20 16.5 42