70. Forensic scientists are often interested in making a measurement of some sort on a body (alive or dead) and then using that as a basis for inferring something about the age of the body. Consider the accompanying data on age (yr) and %

D-aspertic acid (hereafter %DAA) from a particular tooth

(“An Improved Method for Age at Death Determination from the Measurements of D-Aspertic Acid in Dental Collagen,”

Archaeometry, 1990: 61–70.)

Suppose a tooth from another individual has 2.01%DAA.

Might it be the case that the individual is younger than 22?

This question was relevant to whether or not the individual could receive a life sentence for murder.

A seemingly sensible strategy is to regress age on %DAA and then compute a PI for age when %DAA
2.01.

However, it is more natural here to regard age as the independent variable x and %DAA as the dependent variable y, so the regression model is %DAA

0
1x . After estimating the regression coefficients, we can substitute y*
2.01 into the estimated equation and then solve for a prediction of age xˆ. This “inverse” use of the regression line is called “calibration.” A PI for age with prediction level approximately 100(1  )% is xˆ  t(2,n2
SE where SE

1 Calculate this PI for y*
2.01 and then address the question posed earlier.