Store this idea away for a moment of drowsiness: The coffee nap. A coffee nap is when you drink a cup of coffee and then take a 20 minute nap. There's a fun 2-minute video here produced by Vox. Watch the whole thing--it shares the neural mechanism behind drowsiness and explains why caffeine works.
Now, scroll back through the video to the line graph (a pink background) depicted at minute 1:29 and pause the show.
Focus only on the last time period--the end of the four lines. There are clearly four conditions in this experiment, and they represent a factorial design.
a) If there are four conditions in a factorial design, it must be a 2x2. What is the first independent variable? What are its levels? What was the second independent variable? What are its levels?
b) Do you think each IV was manipulated as independent groups or within groups?
c) What is the dependent variable here?
d) Look only at the end of the lines--the data for the last time period only. See if you can regraph the four drowsiness means at this last time period, using a line graph or bar graph. Your graph should be modeled off of those in Chapter 12, with one IV on the x-axis and the other IV represented as line colors.
e) Now that you have your new graph, do you see an interaction in these data? If there is not an interaction, it means the "coffee nap" effect is a simple addition of the "coffee effect" and the "nap effect." (That is, there would be two main effects and no interaction). But if there is an interaction, it would mean that the coffee nap is an extra-powerful combination, stronger than the coffee or the nap simply added together. What's your conclusion?
Bonus:
e) If you scroll back in the video a little further, to the bar graph at 1:17, there's a condition missing. Which condition is missing? Why do you think the authors left this out? Was this an error? Could this be a different study?
