## Regression: Tree Rings and Measuring Things

Author(s): Greg Wiggins1, Suzanne Lenhart2

1. Department of Mathematics, University of Tennessee, Knoxville 2. University of Tennessee

Summary:
Students develop scatter plots of growth rings by tree diameters and determine the equation of their best fit line.

Version 1.0 - published on 03 Apr 2021 doi:10.25334/C4R8-ZN66 - cite this

#### Description

Assemble students in groups of 2‐3 with a calculator and ruler for each group. Using the sheet ‘Example: Regression’ have the students examine the scatter plot of growth rings by tree diameter. Have the students consult and draw an approximate best linear fit line through the points. Have them compare the position of the line, the y‐intercept, and the nearest (x, y) coordinates to those in the associated ‘Calculations’ section. How well did they approximate the line?

Next, explain they will be measuring biological data and calculating variables to exactly determine the mean x and y coordinates, slope, and y‐intercept. To compare their calculations to their estimation skills, have the students measure the diameter and count the growth rings of the sample trees on the ‘Regression Exercise’ sheet, entering the data into the table provided. Next have students plot the data. Then have the students calculate the mean of the x data and the mean of the y data. Have the students draw their own line of the best fit.

This module is part of a collection of educational materials developed for use in teacher workshops and classrooms. The target student audience is listed on each file. These activities include a combination of math concepts and biology applications, ranging from elementary school to Algebra 1 level.

We encourage users to modify and share their adaptations of this module. Please feel free to ask questions or make suggestions in the comments area.

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