Lab 2: Tracks of a Killer

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OBJECTIVES

  • Determine if there is a relationship between the length of a person’s stride and his or her height.
  • Determine if there is a relationship between the size of a person’s shoes and his or her height.
  • Efficiently gather data to test for correlations between height, shoe size, and stride length.
  • Use a linear regression model of the data to predict height based on stride length.

PROCEDURE

Part I: Collecting Data

  1. You’ll need a person to work with for this part.
    1. Use a tape measure or meter stick to measure your height to the nearest 0.01 m, and record it below.
  • Next, remove your right shoe and turn it over. Use a ruler to measure the distance from the tip of the toe to the end of the heel. Record the length of the shoe in meters below.

Next, mark a starting line with chalk or tape. Stand with the backs of your heels at the edge of the starting line. Starting at this point, take 10 normal-length walking steps in a straight line (see the diagram below). After the 10th step, stop and bring your heels together. Mark the final position of the back of the heels and measure the distance to the nearest 0.01 m between that mark and the edge of the starting line. Calculate the average stride length by dividing this distance by 10. Record your average stride length to the nearest 0.01 m below.

2. Repeat step 1 for another person.

ANALYSIS

  1. Enter the data recorded in the Evidence Record below. Ensure all measurement units are consistent for an accurate data analysis. (2 pts)
NameHeight (m)Shoe Length (m)Stride Length (m)
    
    

POST-LAB QUESTIONS

  1. Using figures 1 and 2 below, complete the following: (2 Points Each)

Equation describing the relationship between stride length and height:

Correlation value for stride length vs. height length:

Equation describing the relationship between shoe size and height:

Correlation value for shoe size vs. height:

  • What is the correlation value for the straight line that best describes your data for student stride length vs. height? Do you think the straight line fits these data well? Explain in detail. If you are unfamiliar with the term correlation coefficient, please see the following link: Correlation Coefficient(6 Points)
  1. Based on your data, is there a linear relationship between student height and shoe length? Why or why not? Explain in detail. (4 Points)
  1. Do you think that it is possible to infer a person’s height from his or her shoe size? Why or why not? Explain in detail. (4 Points)
  1. Using the relationship between height and stride length that you calculated, calculate your approximate height and the height of the other person.  You must show your work in order to receive full credit.  Compare the calculated value to the actual value by calculating the % error.  (6 Points Each)

Calculated value your height _____________         % error ____________

Calculate value test subject height ____________   % error ____________

percent error =        x 100%

  • Suppose you measure the stride length of a set of footprints, you predict that the person who made the footprints is 1.75 m tall, and you later find out that the person who made the footprints is actually only 1.52 m tall. Give possible reasons that your prediction was incorrect. Be detailed in your response. (5 Points)  
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