8.8 Assignment

You are a researcher who is interested in the effect of caffeine on anxiety. You recruit 40 undergraduates to take part in your study. Each participant comes to your lab on two consecutive mornings. They drink a cup of coffee, which is regular coffee (containing caffeine) one one day and decaffeinated coffee on the other day. The participants receive the regular and decaffeinated coffees in a random order, and they do not know which beverage they are consuming.

After 30 min (the time necessary for caffeine to take effect), participants complete a measure of state anxiety from the State-Trait Anxiety Inventory. Sample items include “I am tense” and “I feel strained.” This measure produces anxiety scores on a scale from 20 (low anxiety) to 80 (high anxiety).

Your dataset contains the following variables:

  • id: Research ID
  • caff: Anxiety score on the day the participant drank regular coffee
  • no_caff: Anxiety score on the day the participant drank decaffeinated coffee

Download your dataset from Canvas in the folder for this lab. Your dataset is labelled with your name. It is important that you download only your data, since it is different from other students’ data.

You hypothesize that participants will report higher levels of anxiety when they are in the caffeine condition versus the no caffeine condition. Conduct a paired samples t test to test this hypothesis. Report your results in APA format.

As a reminder, you must complete this assignment independently, with no assistance from your classmates.