Lab 07: t-tests

PSY 203: Lab 7.

The primary website for this course is https://faculty.bard.edu/~jdainerbest/psy-203

These are all of the instructions for Lab 7. The list of labs is here.

This website contains R lab code for labs in Bard College’s Fall 2020 for Statistics for Psychology, taught by Prof. Justin Dainer-Best.

You will download the lab’s files to your computer or to your rstudio.cloud account.

Objectives

This lab explores how to “manually” (i.e., step-by-step) calculate the components required for hypothesis-testing with a t-test for dependent means, and then breaks down the use of the t.test() function in R. It also practices using {ggplot2} to create point and bar graphs to visualize data from such a test, including error bars. It also introduces the use of the {dplyr} mutate() function and the the {tidyr} pivot_longer() function.

Make sure you’re in the right working directory

Set your working directory if necessary. Check that you’re in the directory you expect by running getwd() in the Console. If you need more help, look at the wiki page on setting a working directory.

Today’s lab

To download and then run the tutorial, run the following two commands. Please note: only run the usethis::usezip() line once! Running it again will result in your overwriting the files on your computer—potentially losing your work.

Make sure you run the whole command, all the way to the closing parenthesis.

usethis::use_zip(paste0("https://github.com/jdbest/",
                        "psy-203/raw/master/lab07.zip"), 
                        cleanup = TRUE)
rmarkdown::run("lab07/t-tests.Rmd")

Once you’ve completed the tutorial, close it and double click on the visualizing-data-ii-exercises.Rmd file in the folder you downloaded. (You may need to close the tutorial window.) To work on the exercises with the tutorial running, refer to the instructions on the wiki.