Instructions

As a group, you’ll be working with the redbacked salamander (Plethodon cinereus) data again.

Reminder: the data include various measurements of salamanders at several sites in Ithaca, NY. These variables within the data set include:

  • Date of collection
  • Collector
  • Year of collection (2014)
  • Season of collection (limited to Fall for this dataset)
  • Site (A, B, C, D)
  • Snout-to-vent length (SVL) in mm
  • Total length in mm
  • Sex (male, female, or unknown)

For this exercise, you use the ‘Total_length’ column as the response variable of data.

Research Questions

We will try to answer these two questions:

  1. Is there a correlation between SVL and Total_length (from your exercise last week)
  2. Is there an association between Site and Sex?

Analyses and R-Script

To answer these questions you will:

  • Conduct a correlation analysis on SVL and total length in R.
  • Build a contingency table for Site and Sex.
  • Conduct a chi-square test

To build your contingency table, check out the table() function. Try passing it the columns for site and sex to see what happens!

You can use this table in your chi-square analysis.

Your group’s R-script must contain your correlation and association tests.

As with previous assignments, the R-script you submit needs to be appropriately formatted and must run on my computer!

Report

Your group will produce a short report (1 - 2 pages) in which you will present the results of your correlation and association tests.

For the results of the correlation test, you need to address:

  1. Which test did you use for the correlation and why?
  2. What is the evidence (or lack of) for a correlation?
  3. A visualization of the correlation.
  4. A description of the correlation in non-technical terms.
    • This description must use language that a non-scientist or non-statistician would understand.
  5. (Optional) What are the slope and intercept?

For the association test, address the following:

  1. What is the evidence (or lack of) for an association?
  2. What does the association mean, in non-technical terms?
    • This description must use language that a non-scientist or non-statistician would understand.

Submission instructions:

  1. You may submit your report as an html file or a pdf document.
    • Note: you may have trouble knitting your RMd file into a pdf document. In that case, simply use the html option.
  2. One submission per group