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Week 1 · Assignment: Traditional alternative (no AI)

Week 1 — Planning a Fair Sample: A Short Field Report — Traditional alternative (no AI)

Introduction to Statistics 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Traditional alternative (no AI), unpublished. In the course this is a separate assignment that ships unpublished beside the adaptive assignment: same objective, no AI.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 1 of the term — plan a fair sample from a real field log and explain your plan to someone new to statistics.

This week you learned how a sample is chosen and why the choice matters more than the size. In this assignment you work four short problems on a real field log, interpret each one, and explain a sampling plan to someone who has never studied statistics. This week's lecture tutorial, quiz, discussion, and Data Lab practise the same ideas from other angles.

The task

A follow-up research team wants to revisit some of the penguins in the Palmer penguins field log, a real observational dataset of 344 penguins: 152 Adelie, 68 Chinstrap, and 124 Gentoo, recorded on three islands (Biscoe 168 birds, Dream 124, Torgersen 52). Every Chinstrap was logged on Dream, every Gentoo on Biscoe, and the Adelie on all three islands. For this follow-up question, the 344 logged penguins are the population.

Work these four problems, showing your arithmetic:

  1. A stratified plan revisits one in every 4 of the 344 logged penguins within each species. How many of the 152 Adelie penguins does it revisit?
  2. A systematic plan takes 43 of the 344 logged penguins by choosing every k-th bird after a random start. What step k does it use?
  3. Of the 344 penguins in the field log, 11 have no recorded sex. How many penguins have a recorded sex?
  4. A cluster plan visits every logged penguin on Biscoe (168 birds) and Torgersen (52 birds). How many penguins does it visit?

Beside each answer, add one brief interpretation: what that plan or count does, and one use or limit of it for the follow-up visit. For problem 4, say which species the cluster plan leaves out and why.

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

Explain it to a non-expert

The team's volunteer coordinator has never studied statistics and must choose one of the three plans. Write a 3–5 sentence message that recommends one plan, gives a reason tied to these data, and names one limit — including that the original field log is an observational study, so the follow-up visit can describe the penguins but cannot show what causes their differences. Explain any technical term in everyday words. More than one recommendation can be defensible.

For a different, ungraded example, imagine a city library that wants patron opinions and keeps separate lists of adult and teen card holders. Model answer: "I'd pick patrons at random from each list separately. That way both adults and teens are sure to be heard, instead of whoever happens to walk in that day. It still won't tell us what people who never use the library think, and it can't show that a new program caused any change in their opinions."

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

Deliverables

Submit a single field report containing:

  • the four answers, each with the arithmetic shown and a brief interpretation of what that plan or count does and one use or limit for the follow-up visit;
  • your message to the coordinator, recommending one plan with a reason tied to these data and naming one limit; and
  • a one-line restatement of the counts 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 sketch of the three plans 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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