Two-sample t-tests: Independent & Dependent Samples
BEFORE YOU BEGIN:
The videos below will walk you through the following .rmd file: https://drive.google.com/file/d/1eMljicS3xyfRDpuw_OACsBfrR8KzadTD/view?usp=sharing
Be sure you already have the datafile from Ch. 9 saved.
TABLE OF CONTENTS:
16–A: Introduction and Learning Outcomes
If you need a refresher on independent samples t-tests, please see: https://sites.google.com/umd.edu/statisticsinsocialsciences/19-nhst-with-independent-samples-t-test
In this module, we will be learning how to:
Determine the appropriate t-test to run based upon our data.
Assess whether our data meets the assumptions for the t-test we want to run.
Conduct an independent samples t-test.
Conduct a dependent samples t-test.
Calculate the Cohen's d effect size.
Interpret the results of our t-test analyses.
Depict the results of a t-test visually.
Video (0:43)
16–B: Installing/ Loading Packages and Dataset Information
Note that when working through the .Rmd files, R packages will often need to be installed, and libraries loaded. Do NOT quit R while installing or loading packages and libraries. This can corrupt crucial files. Instead, you can STOP the process (by clicking the red stop sign in the upper right corner of the console) and then quit the program, or wait until the process has been completed.
Video (8:01)
16–C: Independent vs. Dependent Samples
Video (1:53)
16–D: Notes About the t.test() function
Video (2:28)
16–E: Independent Samples Question and Hypothesis
Video (1:57)
16–F: Independent Samples Assumptions
Video (10:48)
16–G: Independent Samples Analysis and Interpretation
Video (5:07)
16–H: Cohen's d for Independent Samples
Video (5:12)
16–I: Dependent Samples Question and Hypothesis
Video (1:58)
16–J: Dependent Samples Assumptions
Video (5:54)
16–K: Dependent Samples Analysis and Interpretation
Video (7:29)
16–L: Cohen's d for Dependent Samples
Video (4:39)
16–M: Depicting t-test Results Visually
Video (7:28)
16–N: RMD Analyses Template
To run a dependent samples t-test in R you can use this RMD template:
https://drive.google.com/file/d/1DnNuR-xXeJjqJLlEaF0_SUB2Hi8yuxJA/view?usp=sharing
To run an independent samples t-test in R you can use this RMD template:
https://drive.google.com/file/d/1Xmm_VbmGXwfMBRfH-8NcX6xDin4FgCvp/view?usp=sharing
References
R version 4.1.0 (2021-05-18) -- "Camp Pontanezen". Copyright (C) 2021 The R Foundation for Statistical Computing Platform: x86_64-w64-mingw32/x64 (64-bit)
RStudio Team (2020). RStudio: Integrated Development Environment for R. RStudio, PBC, Boston, MA URL http://www.rstudio.com/.
Tomlinson, T. Jones, B. and Chicoli, A.Statistics in Social Sciences https://sites.google.com/umd.edu/statisticsinsocialsciences