Using Mathematics to Understand Our World s1

Using Mathematics to Understand Our World

Project 2

Notes for the Instructor

Section 1: A Little History and One Method

When writing up this project, students frequently forget to include an explanation of tmax
and tmin , and (again) to not clarify that t is the time since the body was found.

Students had a significantly difficult time (initially) coping with the Marshall and Hoare formula, even though the questions referring to this formula were primarily “plug and chug” type problems. Perhaps the “messiness” of the formula was intimidating.

When using the program at pathguy.com it is important to put in exactly the right information. For example, if "fully clothed, thick bedspread" is entered as the covering option instead of “more layers” you will get the wrong answer (see Solution to the John Boddy mystery). One could adjust the information in the mystery and therefore in the pathguy program to accommodate other choices --- some perhaps more sensible than those described in the accompanying solution. As it stands, the information entered into the pathguy program is as follows:

98F when body was found
300 pounds for the body
still air, dry body
more layers
70F for the room temp
5:00pm time body was found
“no rigor mortis” in Check any that apply

This should result in about 6.6 hours as the time since death. However, since
rigor mortis usually begins to set in around 6 hours (which will need to be mentioned to the students), this sets the death immediately after his talk.

Section 2: A Little Statistics Never Killed Anyone

Students struggled with comparing the methods identified in this section. Some averaged the signed errors rather than the absolute value of the errors. Furthermore, it was necessary to point out that a linear model is reasonable (as a best approximation) since the exponential function is nearly linear for part of the time.