Weight-Length Relationship

Inch Lake

Fit a weight-length relationsip for Inch Lake Largemouth Bass.

Derek H. Ogle


Mar 8, 2019


Feb 13, 2023


This exercise is a continuation of this data wrangling exercise and, thus, depends on data frames constructed there. Please load/run your script from that exercise to access the Largemouth Bass only data frame.


Basic Analysis

  1. Construct graphs appropriate to answer the following questions.1
    1. Describe the relationship between weight and length (in mm here and throughout).
    2. Describe the relationship between log-transformed weight and length.
  2. From the plots above there is a clear minimum length for which the weights were precisely obtained. What is that length? [Reduce the data frame to fish greater than this minimum length for the questions below.]
  3. Compute the weight-length relationship with an appropriate linear regression.
    1. Plot the results (data and the fitted relationship) on both the transformed and raw scales.2 Comment on the fit.
    2. Construct a residual plot.3 Comment.
    3. Express your results as an equation on the transformed scale.
    4. Express your results as an equation on the raw scale.
    5. Carefully interpret the meaning of the slope of the weight-length relationship.
    6. Is there statistical evidence for isometric or allometric growth?

1 If you completed this graphing exercise then you created the necessary graphs there.

2 This post may be useful.

3 This post may be useful.



  1. Recompute the weight-length relationship using the original length in inches. How do the slope and y-intercept from this model compare to the results from the previous question?


Solution Code:

Available upon request to students not in a class. Contact fishR maintainers.