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Week 13 · Assignment: Traditional alternative (no AI)

Week 13 — Sleep Better Tonight? Testing the Claims Behind a Sleep Spray — Traditional alternative (no AI)

Critical Thinking Free sample edition
Traditional alternative (no AI), unpublished. In the course this is a separate assignment that ships unpublished beside the adaptive assignment: same objective, no AI. An instructor who prefers it publishes it and unpublishes or deletes the adaptive one, as the note at its top says.

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

Assignment 12 of the term — test the claims behind an illustrative product ad: ask what its own study was compared with, read a blinded trial against a placebo, see what testimonials can and cannot show, sort the warning signs from the evidence, and explain to someone new what the trial really shows.

This week you learned to ask what would show a claim wrong, to read a failed prediction as modus tollens and a passed one as support rather than proof, to ask what a study was compared with, to tell testimonials from a controlled test, and to treat warning signs as reasons to investigate. In this assignment you work four short problems on one illustrative ad, interpret each one, and explain to someone who has never studied critical thinking what the evidence really shows. This week's lecture tutorial, quiz, discussion, and Argument Workshop practise the same ideas from other angles.

The task

Your text is an illustrative ad for a sleep spray, with no real company, product, store, or customer behind it: "Sleep better tonight! Dozens of happy customers have written in to say they fell asleep faster. In our own study, 35 of 50 users said they slept better, so the spray works. It works through a calming frequency that no sleep lab can measure. Big pharmacy chains don't want you to know about it. And no one has ever proven that the spray does not work. So every student should use it during finals."

Later, an independent trial randomly assigned 100 adults: 50 got the spray and 50 got a look-alike spray with no active ingredient, and neither the adults nor the staff who asked about their sleep knew who got which. In the trial, 34 of 50 spray users and 30 of 50 placebo users said they slept better. The company's sales records show it sold 2,400 bottles, and 36 buyers wrote in to praise it.

Work these four problems, showing your arithmetic and quoting the sentences you use:

  1. In the company's own study, 35 of 50 users said they slept better. What percent of those users said they slept better?
  2. In the blinded trial, 34 of 50 spray users and 30 of 50 placebo users said they slept better. By how many percentage points did the spray group's share exceed the placebo group's share?
  3. The company sold 2,400 bottles, and 36 buyers wrote in to praise the spray. What percent of buyers wrote in?
  4. In the blinded trial, 30 of 50 placebo users said they slept better. If the same share of all 2,400 buyers would say they slept better with no active ingredient at all, how many buyers is that?

Beside each figure, add one brief interpretation:

  • Problem 1: name the conclusion the ad's claims are offered to support and two of the premises offered for it, and explain why the company's own study, with no comparison group, placebo, or blinding, cannot show that the spray caused the better sleep.
  • Problem 2: explain what the control group, the placebo, and the blinding add, say the trial's verdict in words, and name the form of the ad's step from "users said they slept better" to "so the spray works".
  • Problem 3: say what kind of evidence the buyers' letters are, explain why letters from the buyers who chose to write are not a test, and say what the letters cannot show.
  • Problem 4: name at least two of the ad's warning signs of pseudoscience and say why they are reasons to investigate rather than proof, name the fallacy in "no one has ever proven that the spray does not work" and say who carries the burden of proof, and then write the message to the roommate described below.

Explain it to a non-expert

A roommate reads the ad the week before finals and asks, "It says most users slept better and dozens of people wrote in, so it works, right?" Write a 3–5 sentence message that explains in everyday words what the blinded trial shows, reports how many percentage points separated the spray group from the placebo group and how many of the 2,400 buyers would likely report better sleep with no active ingredient at all, and names one limit: the trial is one test of one group of adults, and it does not settle every question about sleep. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a gym sign that says "30 members say our stretching class ended their back pain!" Model message: "Those 30 stories are real, but back pain often eases on its own, so the stories can't show the class did it. A fair test would compare members who take the class with similar members who don't, chosen at random. Until then, the sign is a reason to try the class if you enjoy it, not proof that it works. It also doesn't say how many members took the class and felt no change."

Use that pattern for the roommate, with your own wording and evidence.

Show your arithmetic, write each term out in full, and quote the sentences you use. A reader should be able to reproduce every number you report, and find every quoted sentence in the ad, without guessing which values, steps, or sentences you used.

Deliverables

Submit a single report containing:

  • the four figures, each with the arithmetic shown and the brief interpretation the task names for that problem;
  • your message to the roommate, explaining what the blinded trial shows, with the gap in percentage points and the number of buyers who would likely claim better sleep with no active ingredient, and naming one limit; and
  • a one-line restatement of the values you used (the company's study counts, the two trial groups, the bottles sold and the letters received), so your figures are reproducible.

Keep it to roughly one page.

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 sketch that sets the company's own study beside the blinded trial and marks what each one was compared with, with a short note that says each verdict in words. 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. Quote the ad only as it is printed here, word for word. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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