Week 9 — A Score and a Label: Reading Two Numbers Carefully — Traditional alternative (no AI)
Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.
Assignment 8 of the term — read the IQ scale and a framed food label with careful arithmetic, explain what each number does and does not say, and help a worried parent read a test-score letter.
This week you learned how the mind sorts the world into concepts, solves problems with algorithms and heuristics, and makes fast judgments that are usually useful and sometimes predictably wrong. You also learned three views of intelligence and how the IQ scale is built. In Week 2 you learned that a measure must be reliable and valid; this assignment applies those two words to intelligence tests. You work two short problems, interpret each one, and explain a test-score letter 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
Two numbers this week are easy to read quickly and easy to overread. The first is the IQ scale: intelligence tests are standardized on a large sample and scaled so that the mean score is 100, one step of spread is 15 on the score scale, and about 68% of people score between 85 and 115. The second is a food label: one yogurt says "90% fat-free," and the one beside it says "10% fat."
Work these two problems, showing your arithmetic:
- IQ tests are scaled so that the mean score is 100, and one step of spread is 15 on the score scale. What score marks the lower edge of the average band, one step below the mean?
- A yogurt label reads 90% fat-free. Out of every 100 parts of the yogurt, how many parts are fat?
Beside each answer, add one brief interpretation and one limit. For problem 1, explain what standardization means for this scale, what a score inside the 85 to 115 band says about a person compared with the standardization sample, why a useful test must be both reliable and valid, and why the score is not a measure of the person's worth. For problem 2, explain why "90% fat-free" and "10% fat" state the same fact, name the bias that makes the two labels feel different, and say how that bias differs from confirmation bias.
Explain it to a non-expert
A neighbor who has never studied psychology received a letter saying their child's intelligence test score fell inside the average band, and they worry it means the child is "only average." Write a 3–5 sentence message that explains, in everyday words, what the average band means, what the score does not tell them, and one limit of the test. Explain any technical term in everyday words, and do not guess or invent any real person's score.
For a different, ungraded example, imagine a coworker who will not fly after a week of news stories about one airline's problems. Model answer: "Those stories are vivid and recent, so they come to mind easily, and anything that comes to mind easily feels common. That shortcut is called the availability heuristic. The news reports the rare problem, not the many ordinary flights, so ease of remembering is a poor guide to how often something happens. I can't tell you the exact risk, though; for that you'd need the overall numbers, not the headlines."
Use that pattern for the neighbor, with your own explanation and evidence.
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.
Deliverables
Submit a single brief containing:
- the two answers, each with the arithmetic shown and a brief interpretation and one limit;
- your message to the neighbor, explaining in everyday words what the average band means, what the score does not tell them, and one limit of the test; 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 brief as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labelled sketch of the IQ scale's average band 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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