Counting Grass as a Rich Introduction to Population Estimation

Abstract

Undergraduate students often have trouble grasping concepts of statistical inference and sampling. The activity described here is designed to help students connect their intuition about estimating population sizes to statistical terminology and procedures, and to shed light on some of their misconceptions about sampling techniques. On the first day of an undergraduate Natural Resources Measurements course, students are given 45 minutes to estimate the number of blades of grass covering a large field using rulers and measuring tape. This simple activity is a microcosm of what students will be doing throughout the course, and it provides a basis for rich discussion of many aspects of statistical sampling and population estimation, including random and stratified sampling, variability, error, bias, and decisions about plot and sample size. The activity can also be used to highlight professional skills, such as collaboration and the need for clear communication, and begin the transformation from thinking like students to thinking like professionals. Instructors can easily vary the emphasis on particular topics, depending on course goals and serendipity during the activity. Of significant pedagogical value, this activity is referred to throughout the semester as the intuitive base for statistical concepts that might otherwise get lost in terminology and symbols, and during discussion of professional development.