Week 1 — Reading a Controlled Experiment: The Penny Lab Report

Assignment 1 of the term — read a controlled experiment from its numbers to its conclusion and explain it to someone new to biology.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based lab 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 Biology Lab & Inquiry practise the same ideas from other angles; this assignment is where you put them together on one small experiment.

The task

A penny was filled one drop at a time with water until the dome of water spilled over the edge. The drops on a penny experiment is an illustrative dataset constructed for this course (not real data). Three trials used plain water and held 28, 30, and 32 drops. Three trials used soapy water and held 12, 14, and 16 drops. The plain-water average is 30 drops and the soapy-water average is 14 drops.

Work these four problems, showing your arithmetic:

1. Add the three plain-water trials from the drops on a penny experiment (28, 30, and 32 drops). What is the total, in drops?
2. The three soapy-water trials total 42 drops. Divide by the number of trials (3). What is the soapy-water average, in drops?
3. Plain water averaged 30 drops and soapy water averaged 14 drops. How many fewer drops, on average, did the penny hold with soap?
4. The largest plain-water trial held 32 drops and the smallest held 28 drops. What is the range of the plain-water trials, in drops?

Beside each answer, add one brief interpretation:

• Problem 1: name the independent variable and the dependent variable, and explain why the experiment runs three trials per condition instead of one.
• Problem 2: name the control group and explain why the soapy-water result means something only when compared with it.
• Problem 3: express the difference as a share of the control's average, showing the division, and name one confound, a second difference between the groups, that the design must keep out.
• Problem 4: compare the spread of the trials with the gap between the averages, then write a one-sentence conclusion that uses "supports" or "fails to support" rather than "proves," and name one result that would have counted against the hypothesis.

Explain it to a non-expert

Your roommate sees the penny on the counter and asks, "So does soap make water weaker, or was it luck?" Write a 3–5 sentence message that explains what the test changed and what it measured, reports the result in everyday words, and names one limit, including that these numbers are illustrative and that three trials can support a claim but never prove it. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a café that tests whether a new lid keeps coffee warmer on a walk. Model answer: "We tried two kinds of cups on the same walk, changing only the lid, and checked how warm the coffee felt at the end. The cups with the new lid stayed warmer each time we tried. The weather and the walk were the same for both, so the lid is the likely reason. We only tried it a few times on one day, so the result supports the idea but does not prove it; a cold, windy day might change things."

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

Part 1 — Student instructions

1. Draft all four answers, the four brief interpretations, and your message to your roommate 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 for an introductory biology course. Draw out and challenge MY thinking about reading a controlled experiment. Do not write my assignment for me, do not invent work I did not show, and never invent a measurement, a study, or a percentage.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. The data: the drops on a penny experiment, an illustrative dataset constructed for this course (not real data). A penny was filled one drop at a time until the water spilled. Plain water held 28, 30, and 32 drops; soapy water held 12, 14, and 16 drops. The plain-water average is 30 drops and the soapy-water average is 14 drops.
PROBLEM P1: Add the three plain-water trials from the drops on a penny experiment (28, 30, and 32 drops). What is the total, in drops?
PROBLEM P2: The three soapy-water trials total 42 drops. Divide by the number of trials (3). What is the soapy-water average, in drops?
PROBLEM P3: Plain water averaged 30 drops and soapy water averaged 14 drops. How many fewer drops, on average, did the penny hold with soap?
PROBLEM P4: The largest plain-water trial held 32 drops and the smallest held 28 drops. What is the range of the plain-water trials, in drops?
After the four answers, I must briefly interpret each one: for P1, the independent and dependent variables and why there are three trials per condition; for P2, the control group and why the soapy result needs it; for P3, the difference as a share of the control's average with the division shown, plus one confound the design must keep out; for P4, the spread of the trials against the gap between the averages, a one-sentence conclusion that uses supports or fails to support rather than proves, and one result that would have counted against the hypothesis. I must then write a 3-5 sentence message to my roommate explaining what the test changed and measured, the result in everyday words, and one limit, including that the numbers are illustrative and that three trials support but never prove a claim. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct computations (40 points), biological 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 roommate message only with P4, not again with P1-P3.
COMPUTATION UNITS: A correct total, average, difference, or range = 2; the right values and operation with only an arithmetic slip = 1; a missing result or the wrong values or operation = 0. Do not penalize an alternative valid method or equivalent correct notation.
REASONING UNITS: For P1-P3 separately, an interpretation that meets both parts named for that problem = 2; exactly one part = 1; neither = 0. For P4, BOTH a conclusion that compares the spread with the gap and uses supports or fails to support AND a roommate message with the result in everyday words and a named limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; swapping the independent and dependent variables, calling the soapy-water group the control, or saying the data prove the hypothesis is not accurate. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone new to biology, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the roommate message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING-WORK UNITS: For each problem, checkable values and steps = 2; a relevant but incomplete value 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 message to my roommate 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 lab report, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised lab report with all four answers, their brief interpretations, and your message to your roommate — written, or recorded as audio or video with a transcript, or as a labelled sketch of the six trials 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 — naming the parts of a controlled experiment, computing averages, a difference, and a range with every step shown, reading the result against the control group, and stating an honest conclusion — 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 your roommate. 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 lab 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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