Week 5 Hypothesis Testing Concepts

This week we introduce hypothesis testing - a very important concept and methodological framework.

5.1 What we cover this week

  • The null and alternative hypotheses
  • P-values
  • Significance level
  • Test statistics
  • Type I and Type II errors
  • One and two-tailed tests

5.2 Readings

Chapter XI in online textbook

Key sections:

  • Introduction
  • Significance Testing
  • Type I and Type II Errors
  • One- and Two-Tailed Tests
  • Interpreting Significant Results
  • Interpreting Non-Significant Results

5.3 Lab

This week’s lab is a little different. Instead of calculating quantities from data (which we will do next week, don’t worry), we are going to focus on intepreting existing research results, to get a feel for how these tools are actually used. In particular, we are going to focus on a t-test for a sample mean, and hypothesis tests about sample means.

Your first objective will be to find a scientific paper that interests you. Go to google scholar and to search enter “t-test” AND “something that you want to read research about”. Make sure you include the quotation marks. For example I will use “t-test” AND “polar bears” just to get started. This brings up this page of search results. Now you probably do not want to select the first article you see. You want to select an article based on the following criteria:

  • is it actually about the topic your are intersted in
  • is a t-test for a mean used in the analysis
  • can you understand the paper
  • do you have access to the full text of the paper

You may have to go in through the library website to gain access to a paper, othertimes you will see a link from Google Scholar directly to a PDF of the paper. Your goal is to select a paper of interest which you will then answer questions (below) about for this week’s lab assignment.

On the second page of results, I found the following paper which I thought met the criteria above. T-tests were used here to compare the mean litter size among samples of polar bear cubs in two regions (Hopen Island vs. the rest of Svalbarad), among other things.

5.3.1 Assignment

Once you find a paper you want to work with for this lab, answer the following questions below:

  1. Write a paragraph summarizing your paper. What were the research objectives, what data were analyzed, what did the results show? (out of 5)

  2. What specific hypothesis was tested using a t-test in this paper? Was it upper, lower, or two-tailed? What was the result? Include a screenshot of the result from the paper. (out of 5)

  3. What limitations are there in the study? What other types of analysis or data could the researchers have used to address their objective(s)? (out of 4)

  4. What does the p-value reported in the paper mean? Include a screenshot of the result from the paper. (out of 3)

  5. What was the significance level of the hypothesis test in the paper? What does it mean? Include a screenshot of the result from the paper. (out of 3)