Your goal is this WPA is to create an APA style document using papaja and R Markdown. Make sure you have installed the papaja package with the following code:

# Install papaja from GitHub
devtools::install_github("crsh/papaja")

  1. Create a new R project called studentAPA.RProj somewhere on your computer with File – New Project …. If you don’t know where to put it, put it on your desktop. Open this project!

  2. Navigate to the project directory (the one you just put studentAPA.RProj in). You should see a file called studentAPA.Rproj there. Now, create two new folders R and data in this directory.

  3. In this WPA, you will analyze data from a study on student performance in two classes: math and Portuguese. These data come from the UCI Machine Learning database at http://archive.ics.uci.edu/ml/datasets/Student+Performance#Download. The data are located in two tab-delimited text files at the following locations:

Download the two data files using a web browser and save them as two separate text files called studentmath.txt and studentpor.txt. Save them to the data folder of your project directory! (or you can do it within R using a combination of with read.table() and write.table()).

  1. Using a web-browser, download the following two files and save them to your project working directory – that is, next to the studentAPA.Rproj file. Not in the data or R folders.

STOP!!!

By now you should have a file structure on your computer that looks like the following screenshot

Here is how your RStudio screen should look when you are in the appropriate project. Note that the file structure matches the one on your computer.

If you don’t have this folder structure and/or you don’t have the appropriate project open in RStudio, the rest of the document won’t work!

  1. Your goal is to create this APA document (https://dl.dropboxusercontent.com/u/7618380/studentAPA_comp.pdf) by adding elements to the studentAPA.Rmd document.

  2. Open studentAPA.Rmd and studentAPA.bib. In studentAPA.Rmd, replace the X values in the main fields at the top of the document (name, paper title, short-title, affiliation) with the appropriate names and titles.

  3. Know Knit your document to see the current version of the PDF output! You can do this by clicking the “Knit” button at the top of your window.

  4. Now it’s time to add some references to your studentAPA.bib file! You will be referencing three papers in this document. Using scholar.google.com, find the BibTeX references for the following paper(s) and add them to your studentAPA.bib file. Make sure to save the file!

  1. Now it’s time to cite your new references. I’ve included one citation already in the studentAPA.Rmd document in the format @abedi2001language. Now cite the additional papers in your studentAPA.bib file by replacing the XXX values with the appropriate citations. Knit your document to see the result

  2. You need to load your data in a separate chunk. I’ve already created a chunk with all the code you need. Of course, This code assumes that your data are stored in studentmath.txt and studentpor.txt in a folder called data in your project directory!. To make sure the chunk is evaluated, change eval = FALSE to eval = TRUE in the chunk options. Knit your document to see the result If you don’t see any errors, then the data should have been correctly loaded!

  3. In the Participants section, there are inline code chunks that should indicate the number of participants in each data set. Replace the 1+1 values with nrow(student.por) and nrow(student.math) to get the number of students in each data set. Knit your document to see the result

  4. In the Results section, I’ve included a chunk that creates Figure 1, a series of histograms. Update the caption to the plot in the chunk options. Then change eval = FALSE to eval = TRUE to tell Markdown to run the chunk. Knit your document to see the result You should now see the histograms in your document.

  5. Below the Figure 1 chunk, there are some inline chunks that calculate the mean grades for exam 1 and exam 3 of the Portuguese data. Update these chunks with round(mean(student.por$G1), 2) and round(mean(student.por$G3), 2) to calculate the correct values. Knit your document to see the result

  6. The next two chunks create tables of summary statistics for the Math and Portuguese data. Update the captions in these chunks. Then, change eval = FALSE to eval = TRUE in the chunk options. Knit your document to see the result You should now see the tables in your document.

  7. The next chunk conducts and saves t-tests for both the math and Portuguese data. The code for the Portuguese test is already completed. Fix the code for the math test. Then, change eval = FALSE to eval = TRUE in the chunk options.

  8. The next lines use inline code to refer to the results of your t-test objects. Replace the 1+1 values with values from your t-test!. (Hint: use sex.por.ttest$parameter to get the degrees of freedom, sex.por.ttest$statistic to get the test statistic, and sex.por.ttest$p.value to get the p-value for the Portuguese test). Knit your document to see the result

Add new analyses!

  1. Add a scatterplot showing the relationship between G1 and G3 for the math data as a new Figure. Knit your document to see the result

  2. In addition to your scatterplot, conduct the appropriate correlation test using cor.test() in a separate chunk. Save the result as math.cor.test

  3. Now report the results of your correlation test in your text. You can easily do this using the apa_print() function from papaja. Look at the help menu for apa_print(). Then use the function to report the results of the correlation test by running apa_print(math.cor.test). Knit your document to see the result

Finished!

Save and email your studentAPA.Rmd and studentAPA.pdf files to me at nathaniel.phillips@unibas.ch. Then, go to https://goo.gl/forms/UblvQ6dvA76veEWu1 to complete the WPA submission form.