## Classroom

# Measuring Footprints

Students learn how to calculate their carbon impact.

Despite all the recent media attention given to global warming, a significant number of people either don’t believe the threat or refuse to change their behavior to reduce their overall energy consumption. While the idea of a carbon footprint has lodged itself in the public consciousness, many people still aren’t sure exactly how to compute the impact their actions have on the planet’s resources.

**Lesson description**: Students will learn how their choices for transportation, recycling and energy usage impact the carrying capacity of the planet and the subsequent connection to global warming.

An eco-footprint, also known as a carbon footprint, is the amount of acreage necessary to sustain the food and energy needs of an individual. There are many Web sites that calculate this acreage and then show how much land would be needed if everyone lived in the same manner. It can be a real shock for some students when they see that if everyone on the planet lived the way they do, it would require four or five planets’ worth of acreage to sustain.

Students take 10 minutes to answer the 16 questions about housing, car and plane travel, and food choices on www.earthday.net/footprint. The result: The number of acres required for the choices is calculated, as is the number of planets needed. Now students can analyze their statistics, comparing their individual results with the class average. They then input the individual values for the number of acres into a spreadsheet or graphing calculator. Once done, they can enter the function for average or complete the “one variable statistics” if using a TI 83-84 graphing calculator. If you are working on a computer spreadsheet program, such as Excel, you’ll have to go to separate functions to determine these values. Ideally, the students should produce a box plot or a histogram for the distribution of number of acres needed.

**Subject area**: This is primarily a math lesson (with applications to science) designed for students from grades six through 12. The wide spread of grades can be addressed through varying degrees of statistical analysis, from a simple histogram to box plots, standard deviation and correlation.

**Curriculum Standards**: This lesson meets the California mathematics standards in the area of statistics for grades six through eight but can be taught through grade 12.

Grade 6: Identify different ways of selecting a sample; analyze data displays; identify claims based on statistical data.

Grade 7: Understand the meaning of the minimum, the lower quartile, the median, the upper quartile and the maximum.

Probability and Statistics: Students know the definitions of the mean, median and mode of a distribution of data and can compute each in particular situations.

**Resources**: For online statistical analysis, visit www.shodor.org, click the Statistics tab, and select Box Plot, Bar Graph or Measures (to view the mean, median, variance and standard deviation). Use of a TI 83-84 graphing calculator is optional.

**Grading Rubric**: This activity can be a method to introduce a statistics unit on mean, median and box plots. It can be graded as a single assignment or as part of a larger set of assignments on statistical analysis or environmental awareness.

### Teaching Tips

Before starting the lesson in class, have the students d0 the following:

- calculate the area of their home in square feet;
- determine a major city with weather similar to theirs;
- figure out how many miles per week they travel by car, bike and on foot;
- find out how many miles per gallon their parents’ car gets.

For homework, have students retake the “quiz” by changing the one answer they think has the greatest impact and observing their resulting footprint.