Numerical estimates, such as ballpark figures or “guesstimations,” abound in school, work, and our lives. For example, you can roughly calculate the impact of shopping with a reusable grocery bag, instead of using plastic bags, for a year. But how can anyone know that? How do we make sense of “guesstimations?” Are they even grounded in good mathematical principles?

Our team member Connie Williams shared a video of a talk by Dr. Lawrence Weinstein, a professor at Old Dominion University. In his lecture, “Guesstimating the Environment,” he points out that “guesstimations” are inherently imprecise. He covers the use of “guesstimations” in topics ranging from ethanol to windmills and considers issues by calculating estimates. While “guesstimations” are imprecise, they do provide a way to understand the scope of a problem.

Watching this lecture, or a portion of it, could spark a discussion about “guesstimations” in the news and academic resources with your students. Some questions to discuss include:

  • Where do “guesstimations” appear?
  • What purposes do “guesstimations” serve?
  • What are the limitations of “guesstimations?”
  • What are appropriate uses and applications of “guesstimations?”


Dr. Weinstein also asks a key question about a “guesstimation:”

Is this a lot or a little?

It can be hard to know if a “guesstimations” is big or small. Consequently, Dr. Weinstein emphasizes the need to compare the numbers to something else. A comparison is a great way to make sense of numbers, whether they are estimates, actual counts, probabilities, or statistics. When creating or evaluating “guesstimations,” a helpful rule of thumb is to find something with which to compare it or help to put it in context. In the grocery bag example, he explains how to compare a person’s annual use of plastic bags to gasoline burned by driving her car. It turns out that the amount of plastic bags that an individual uses is insignificant compared to how much gas that her car burns. The lecture contains many more examples like this — have a look!


Image: “Bags Plastic Shopping Household Colorful Sunny” by BRRT, on Pixabay. CC0 Public Domain.