Week 10 · Assignment: Traditional alternative (no AI)

Week 10 — Does the App Cause Better Sleep? Testing Causal Claims in a Newsletter Blurb — 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Traditional alternative (no AI), unpublished. In the course this is a separate assignment that ships unpublished beside the adaptive assignment: same objective, no AI.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 9 of the term — read a survey's pattern as a correlation, check it for a hidden third factor and a backward arrow, catch a cause inferred from order alone, test a chain of predicted consequences link by link, and explain to someone new why a striking pattern does not show that an app works.

This week you learned to tell a correlation from a causal claim, to check every correlation against a confounding factor, reverse causation, and coincidence, to spot after this, therefore because of this, to test a slippery slope one link at a time, and to say what a controlled comparison adds. In this assignment you work four short problems on one illustrative newsletter blurb, interpret each one, keep a fallacy apart from a false premise as Week 7 taught you, and explain to someone who has never studied critical thinking why a striking pattern is not proof. This week's lecture tutorial, quiz, discussion, and Argument Workshop practise the same ideas from other angles.

The task

Your text is an illustrative newsletter blurb for a sleep app, with no real app, company, campus, or student behind it: "Our sleep app works! We surveyed 200 students who use it and 200 who do not: 150 of the app users reported sleeping well, against 90 of the non-users. One user started the app the week before finals and passed every exam, so the app boosts grades too. And if the campus stops paying for the app, students will stop sleeping, grades will fall, and the campus will lose its students."

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

Of the 200 app users surveyed, 150 reported sleeping well. What percentage of the app users reported sleeping well?
Of the 200 non-users surveyed, 90 reported sleeping well. What percentage of the non-users reported sleeping well?
Of the 200 non-users surveyed, how many did not report sleeping well?
Of the 200 app users surveyed, how many did not report sleeping well?

Beside each answer, add one brief interpretation:

Problem 1: say what pattern the survey shows and what causal claim the blurb builds on it, and name one confounding factor that could drive both using the app and sleeping well.
Problem 2: explain how reverse causation could produce the same pattern, and describe a controlled comparison, with students assigned to use the app or not by lottery, that would test the blurb's claim.
Problem 3: name the fallacy in the finals sentence, list two other things that also came before the passing grades, and describe a comparison that would give the claim real support.
Problem 4: list the links in the last sentence's chain, say which links are backed by evidence, and give your verdict on the chain, then write the message to the friend described below.

Explain it to a non-expert

A friend who has never studied logic reads the blurb and asks, "Way more app users sleep well, so the app must work, right?" Write a 3–5 sentence message that explains in everyday words why the survey does not show that the app causes better sleep, reports the percentage of app users and the percentage of non-users who reported sleeping well, and names one limit: the students who chose the app may differ from the others in ways the survey never measured. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a gym flyer that says "Members who take our evening stretch class report fewer sore muscles, so the class prevents soreness." Model answer: "The members who pick a stretch class may already be the ones who warm up, rest, and train carefully, so the class and the low soreness could both come from those habits. It could also run the other way: people with sore muscles may skip a stretch class that week. To know whether the class itself helps, you would need a fair test where chance decides who takes it. Until then, treat the flyer as a reason to look closer, not as proof."

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

Show your arithmetic, write each rival and fallacy name 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 blurb, without guessing which values, steps, or sentences you used.

Deliverables

Submit a single report containing:

the four answers, each with the arithmetic shown and the brief interpretation the task names for that problem;
your message to the friend, explaining why the survey does not show that the app causes better sleep, reporting the percentage of app users and of non-users who reported sleeping well, and naming one limit; and
a one-line restatement of the values you used (the students surveyed in each group and how many in each reported sleeping well), so your answers 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 sketch that shows the two groups of 200 students side by side with how many in each reported sleeping well, 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 blurb 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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