Week 1 — Planning a Fair Sample: A Short Field Report

Assignment 1 of the term — plan a fair sample from a real field log and explain your plan to someone new to statistics.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based field report. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This week's lecture tutorial, quiz, discussion, and Data Lab practise the same ideas from other angles; this assignment is where you put them together on one real decision.

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.

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.

Part 1 — Student instructions

1. Draft all four answers, the four brief interpretations, and your message to the coordinator before opening a chatbot.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Answer in your own words. Show calculations when asked. Use the coach's feedback to revise at least one calculation or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the report for you.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach. Draw out and challenge MY thinking about sampling plans and study design. Do not write my assignment for me and do not invent work I did not show.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. The data: the Palmer penguins field log, an observational dataset of 344 penguins (152 Adelie, 68 Chinstrap, 124 Gentoo) on Biscoe (168 birds), Dream (124), and Torgersen (52); every Chinstrap is on Dream, every Gentoo on Biscoe, and Adelie on all three. For this follow-up visit the 344 logged penguins are the population.
PROBLEM P1: 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?
PROBLEM P2: 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?
PROBLEM P3: Of the 344 penguins in the field log, 11 have no recorded sex. How many penguins have a recorded sex?
PROBLEM P4: A cluster plan visits every logged penguin on Biscoe (168 birds) and Torgersen (52 birds). How many penguins does it visit?
After the four answers, I must briefly interpret each one: what that plan or count does and one use or limit for the follow-up visit; for P4, which species the cluster plan leaves out and why. I must then write a 3-5 sentence message to a volunteer coordinator who is new to statistics, recommending one plan with a reason tied to these data and naming one limit, including that the field log is an observational study. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct sampling computations (40 points), sampling and study-design reasoning (32 points), clarity for a non-expert reader (16 points), and showing work so it can be checked (12 points). For each of P1-P4, give 2, 1, or 0 evidence units per criterion; one unit is worth 5 computation points, 4 reasoning points, 2 clarity points, or 1.5 showing-work points. Sum all four problems within each criterion. Count my final message only with P4, not again with P1-P3.
COMPUTATION UNITS: A correct count or step = 2; the right counts and operation with only an arithmetic slip = 1; a missing result or the wrong counts or operation = 0. Do not penalize an alternative valid method or equivalent correct notation.
REASONING UNITS: For P1-P3 separately, an accurate account of what that plan or count does plus a use or limit tied to the penguin field log = 2; exactly one of the two = 1; neither = 0. For P4, BOTH an accurate explanation of the species the cluster plan leaves out AND a final recommendation with a data-specific reason and a named limit, including that the field log is observational = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; naming a plan alone does not earn a unit. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone new to statistics, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the final message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING-WORK UNITS: For each problem, checkable counts and steps = 2; a relevant but incomplete count or step = 1; a result alone or no method = 0. A visible method stays checkable despite an arithmetic slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my answer. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word answer is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four answers and their brief interpretations AND written my recommendation to the coordinator AND revised at least one calculation or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned score; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the score for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my calculations and reasoning]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised field report, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised field report with all four answers, their brief interpretations, and your message to the coordinator — written, or recorded as audio or video with a transcript, or as a labelled sketch of the plans with a short note; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

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.

Equivalent route (no AI required)

This route assesses the same Week 1 skills — computing and interpreting sampling plans, telling the population from the sample, and explaining what an observational study can and cannot show — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems, the four brief interpretations, and the message to the coordinator. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and write a second draft. Add a 150–200 word revision memo that names one calculation or explanation you changed, the evidence that prompted the change, and one question you still have. Submit the revised field report, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

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

Academic integrity and AI use

The calculations, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment or add evidence you did not produce. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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