Week 2 — What Does the Evidence Allow? A Short Research-Methods Report — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 2 of the term — read four classic studies and one illustrative dataset, work out what each one found, and explain to someone new to psychology what a study can and cannot claim.

This week you learned how psychologists turn a fuzzy idea into a measurement, what each research design is allowed to conclude, why correlation is not causation, and which protections every research participant is owed. Last week you saw why psychology tests its ideas against evidence instead of trusting common sense; this week shows how that testing works. In this assignment you work four short problems on real study results, interpret each one, and explain a headline to someone who has never studied psychology. This week's lecture tutorial, quiz, discussion, and Analysis Workshop practise the same ideas from other angles.

The task

You will use these study results, all from this week's chapter:

• Ebbinghaus (1885) measured memory as percent savings on relearning: savings were 58.2% at 19 minutes and 21.1% at 31 days.
• Loftus and Palmer (1974), Experiment 1: students who heard "smashed" averaged a speed estimate of 40.8 mph; "hit" averaged 34.0 mph; "contacted" averaged 31.8 mph.
• Loftus and Palmer (1974), Experiment 2: a week later, 16 of 50 students in the "smashed" group, 7 of 50 in the "hit" group, and 6 of 50 in the control group, which got no speed question, reported broken glass that was never in the film. Students were randomly assigned to their condition.
• Milgram (1963): 26 of 40 participants continued to the 450-volt switch. They believed the shocks were real; none were given.
• An illustrative dataset built for this course: 10 students reported hours of sleep and their next-day quiz score out of 20, and r = 0.8457. Nobody's sleep was changed.

Work these four problems, showing your arithmetic:

1. Ebbinghaus's savings were 58.2% at 19 minutes and 21.1% at 31 days. By how many percentage points did savings fall?
2. In Loftus and Palmer's Experiment 1, "smashed" averaged 40.8 mph and "contacted" averaged 31.8 mph. By how many mph did the "smashed" estimate exceed the "contacted" estimate?
3. In Loftus and Palmer's Experiment 2, 16 of 50 students in the "smashed" group reported broken glass. What percentage of that group is this?
4. In Milgram's study, 26 of 40 participants continued to the 450-volt switch. What percentage of participants is this?

Beside each answer, add one brief interpretation: what that value shows about the study's design and one use or limit of it. For problem 1, name the operational definition and say why replication matters. For problem 2, label the independent variable and the dependent variable. For problem 3, say what the control group adds and why random assignment lets the study claim a cause. For problem 4, name two protections that today's research rules require for a study like this and say why.

Show your arithmetic. A reader should be able to reproduce every number you report from the values above without guessing which values or steps you used.

Explain it to a non-expert

The volunteer editor of a community wellness newsletter has never studied psychology and wants to print the headline "Study shows sleep raises quiz scores" about the 10-student sleep data. Write a 3–5 sentence message that recommends a more honest headline, explains in everyday words what r = 0.8457 does and does not show, names one third variable that could explain the link, and names one limit of the data — for example, that the dataset is illustrative and small, or that nobody was randomly assigned to sleep more. Explain any technical term in everyday words. More than one honest headline can be defensible.

For a different, ungraded example, imagine a gym manager who read that members who use the sauna report being happier. Model answer: "I'd say 'Sauna users report feeling happier,' not 'The sauna makes members happier.' The study asked people about two things and found they went together, but nobody was assigned to use the sauna. Members with more free time might both use the sauna more and feel happier, so free time could explain the link. A fair test would randomly assign some members to sauna sessions and compare them with members who did not get them."

Use that pattern for the sleep headline, with your own recommendation and evidence.

Deliverables

Submit a single research-methods report containing:

• the four answers, each with the arithmetic shown and a brief interpretation of what that value shows about the study's design and one use or limit of it;
• your message to the editor, recommending an honest headline for the sleep data, explaining what r = 0.8457 does and does not show, and naming a third variable and a limit; and
• a one-line restatement of the values you used, so your results are reproducible.

Keep it to roughly one page. Clear and correct beats long.

Choose how you show it. Present your report as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labelled diagram of each study's design with a short note. Every form is graded by the same scoring criteria. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

This version is designed to be completed without AI: do the computations, the interpretations, and the writing yourself, without a chatbot or other AI tool. You may use a calculator or a spreadsheet for the arithmetic. Submitting AI-generated work as your own, or copying another student's numbers, is an integrity violation under the course policy.

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