Fort Lewis Forensics
a.k.a. Mr. Potato Head
About the Project
The original idea for this project came from Activities for Algebra with the TI-83 Plus by Rachel
Newman-Turner and Robert Goodman. The project is an excellent summative assessment that
covers modeling/regression and transformations.
A terrible crime has been committed. A well respected potato has been murdered. When found,
the temperature of the body was given in degrees Celsius. A healthy potato has a body
temperature of 65 degrees Celsius. In this project, you are to create a model that accurately
models the decrease in temperature of a dead potato over time. This model can then be used to
determine the time of death of future deaths. You will be given your own case and will need to
apply your model to determine the time of death for your case.
You may work in partners for this project. First, you need to record room/ambient temperature.
Now, in order to create your model, you are going to take a medium-sized sacrificial spud and
either boil it for 15 minutes or microwave it on high power for five minutes. Then, using a sharp
pencil or pen, puncture the potato. The hole in the potato should reach to its center. Insert the
end of a thermometer into the center of the potato. You will need to check out a glass alcohol
thermometer from your instructor. The temperature will rise and peak after a few minutes. At
this point, the temperature will start to decrease. Once the temperature reaches 65 degrees
Celsius, record this temperature as time equals zero. Then, record the temperature every five
minutes for the next hour.
Milestones/Due Dates for Project
Data Submission Day (Friday, February 29th) – Your data must be collected and submitted by
this date. Data should be typed and presented in table form with the columns clearly labeled.
Model Creation Day (Wednesday, March 12th) – Complete the attached (see page 2) Model
Creation Worksheet for submission on this day.
Final Report (Monday, March 24th) – See page 3 for details.
Model Creation Worksheet
1. Complete the following table with the original data and provide a scatter plot of the
original data. Be sure to label your axes.
2. Define your variables and, using function notation, provide the linear regression model
for this data.
3. Using function notation, provide the exponential regression model for this data.
4. If you were to use one of your models to determine the time of death of a potato, discuss
the assumptions underlying its use that might affect the validity of the model for a
particular case. In other words, discuss the limitations of each of the models that you
have created. Your discussion should include, but not be limited to, domain & range
limits and asymptotes.
Which model do you feel is more appropriate and why?
Mr. Potato Head Final Report
Using what you found in completing the Model Creation Worksheet, write a final report to the
Durango Chief of Police summarizing the model creation process, the models up for contention
and your final recommendation. Provide tables and graphs of models used during this creation
process. The work done for the Model Creation worksheet has yet to take into consideration
room/ambient temperature. Discuss how your best model might be modified to account for
room/ambient temperature (Hint: see Boston Marathon Problem discussed during class).
Summarize the benefits and limitations of your modified model. Use your model to determine
the time of death for your case. Indicate this point clearly on your graph.
Report Due: Monday, March 24
• Typed – calculations and graphs may be done neatly by hand.
• 12 pt type, Arial or Times New Roman font
• 1 inch margins
• Double spaced
• This rubric needs to be attached to the front of your report when you turn it in.
A Properly formatted (typed, double spaced, attached rubric)
B Complete sentences with proper grammar, spelling punctuation
C Language is precise (limited use of pronouns, correct terminology, etc.)
D Introduction summarizes important information
E Completely and correctly answers the question(s)
All variables are identified (letter, what it represents, units, ind/dep) (if
Equation/formula/model is given and parts of equation are identified/explained
Calculations (if applicable) are introduced verbally and mathematical steps are
I Results of calculations (if applicable) are interpreted in a complete sentence
J Table (if applicable) has title and columns are labeled
Graph (if applicable) has a title, is properly labeled, scales are appropriate and
function and/or data is graphed correctly