Activity B: Correlation

Activity B takes the training wheels off and throws you into the world of inline coding and correlations.

This activity explores correlation and to learn how to create and interpret a scatterplot using R.

The Data

Using content from this website (note that we’re using RStudio, not Excel), here is the context for this activity:

A researcher was interested in whether there was an association between communication skills and quality of peer relationships in third grade classrooms. Teachers in each class completed a communicative skills checklist and a rating scale of peer relations for each child. The items for each scale were averaged to provide an overall score for each child.

Variable names in the provided CSV file:

1. ID = case identification number
2. comm = communication skills
3. peers = quality of peer relations

Steps to completion

Watch the following!

• Scatterplot in RStudio
• How to make a scatterplot in R (with regression line)
• Plotting with ggplot2 to get the basics on how to produce the plots you need below.

Again, we’re using the Posit Cloud Activity B template for this assignment. This is very similar to the Activity A template.

This activity goes well beyond simply displaying frequencies and descriptives for common concepts like means and medians. You will need to dig around the R documentation for the commands to best answer the questions below. For this activity, create and submit a document that includes and answers the following (again, these instructions are preloaded in your qmd):

1. A scatterplot that displays the relationship between the peers and comm variables. Referencing the scatterplot, answer the following:
   1. What does this chart tell you about the relationship between the two variables?
   2. What direction is this association?
   3. How did you determine this?
   4. If you had to identify the association, would you label is small, moderate, or strong? Why?
2. Determine the Pearson correlation for the peers and comm variables. Referencing the Pearson correlation coefficient, answer the following:
   1. Interpret this number.
   2. What is the strength of the association?
   3. What is the direction?
   4. Like the scatterplot above, do you think it is small, moderate, or strong?
   5. How does your interpretation of the Pearson correlation coefficient compare to that of the scatterplot?
3. Determine R² by computing the square of the correlation coefficient you previously calculated.. Using this coefficient of determination, answer the following:
   1. Interpret this value. What does it indicate about the association?
   2. Write a statement about the meaning of the R-squared (R²) value in terms of the variables.
   3. How does R² compare to what you saw in the scatterplot and the Pearson correlation coefficient?
   4. Do you think this is a more valuable statistic? Why?

Submitting

1. Complete the grading declaration quiz in the LMS. Note that this is not the same content that goes into your assignment submission!
2. Submit both your qmd and your HTML file to the Activity B dropbox in the LMS by the stated due date and time.
3. Remember: the point of using this file system is reproducibility. Ensure you haven’t removed the embed-resources: true YAML line!