Variation in Estimates Lab (Fathom)


Fathom Lab

– Variation in Estimates: Meters vs. Feet

In this activity you will see if you and your class estimate lengths more accurately in feet or in meters.


1. Ms. C will randomly split the class into two groups.

2. If you are in the first group (G1), estimate the length of your classroom in feet.

If you are in the second group (G2), estimate the length of the room in meters.

Do this by looking at the length of the room; no pacing the length of the room is allowed.

3. Make a new, empty case table by dragging the table icon from the menu bar across the top of the program to the work area and define two new attributes:




. For each person in your class, enter their group (G1 or G2) and their estimate of the length of the room. Each case

(person) represents a single estimate, identified by the person’s group. (Your table should look similar to the example here.)


Converting the estimates to a common unit is necessary to make an appropriate and meaningful comparison of the two distributions. Fathom can be used to do the unit conversions.

4. Double-click the collection to show its inspector. On the


panel, click <new > and create an attribute called


5. Double-click in the formula cell to show the formula editor. Enter the formula with an “if” statement that will convert the estimates only from the group using feet. (See the example here.) Click


The “if” statement checks whether the case is in G1. If so, it converts the measurement in feet to a measurement in meters. If the case is not in G1, it keeps the original measurement.

6. Make a new graph by dragging the graph icon to the work area and drag


to the horizontal axis. Then drag


to the vertical axis to split the graph into two graphs with the same horizontal axis.

Create a Word document with your name and the name of your partner in the top right corner. Save your document and name it with the last names of each partner separated by an underscore. For example: Dimsdale_Kelly.doc. Answer the following questions in your word document.

Q1. Create parallel boxplots, parallel histograms, and parallel dotplots. Copy each of these displays into your document.

Q2. Describe the two distributions from your class in terms of shape, center, and spread. How are the two distributions similar and how are they different? Note any clusters and gaps or unusual data values (outliers) in either of the distributions. (You do not have to use precise statistics for the center and spread but you should discuss each. For example, which distribution has a larger center? Which distribution is more spread out or has more variability?)

Q3. Do you think the students in your class tend to estimate more accurately in feet or in meters? What is the basis for your decision?

Q4. Why should you split the class randomly into two groups instead of simply letting the left half of the room estimate in feet and the right half in meters?

Submit your completed Word document to my webpage,



enter your first and last name & upload your Word Doc