🔬 Designing a Controlled Experiment — printable rubric packet (Scientific Method & Lab Skills Unit 04). Print 8.5×11 portrait. Every page is designed for clipboard use while you grade during the activity.
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▲ Page 1 — Unit overview
Bright Minds Scientific Method & Lab Skills · Course Pack
Designing a Controlled Experiment — Unit Packet
Overview
v0.1 · Page 1 of 5

Use these targets, vocabulary, rubrics, examples, and score sheet with the instructor's approved lesson and procedure. This is an assessment companion, not a complete lesson or safety authorization.

Unit learning targets

The student demonstrates the following:

How this unit is assessed

Mastery rubric

Five science criteria plus separately reported integration (Page 3).

Fair-test design task

Plan and set up a controlled experiment — watched live.

Oral check

The student defends each design choice aloud (Page 4).

Lab notebook

Design, procedure, and results kept distinct.

How to read a Bright Minds rubric

You are making a decision, not adding up points. For each criterion, decide whether the work is Developing, Proficient, or Mastery — the column language tells you which. A criterion counts as mastered only when the student can both design the fair test and defend why the comparison is fair. Each student has three tokens per term; each token retries one rubric criterion. Approved accommodations, equipment failures, and approved absences are handled separately and do not consume these tokens.

▲ Page 2 — Key terms
Controlled Experiment · Vocabulary
Key Terms — What Counts as Correct
Vocabulary
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Accept listed synonyms; use the distinction column to resolve near-matches.

Canonical answerAccepted synonymsCommon confusion / discriminator
Variables & fair tests
Independent variablewhat you changeThe one thing changed on purpose (lamp vs. window)
Dependent variablewhat you measureThe result you record (seedling height)
Controlled variablewhat you hold steadySame soil, water, pot — so one change explains a difference
Comparison & trust
Control groupuntreated baselineAn identical setup left in ordinary conditions
Fair testplanned comparisonThis introductory design varies one factor; more complex designs need explicit controls and replication
Replicationrepeating the testRepeats guard against a fluke
Sample sizehow many you testToo few can’t tell a real effect from chance
Procedurethe written stepsComplete enough for a stranger to follow exactly
▲ Page 3 — Mastery rubric
Controlled Experiment · Mastery Rubric
Six Criteria — Developing / Proficient / Mastery
Rubric
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CriterionDevelopingProficientMastery
Independent & dependent variablesCannot say what is being changed or what is being measured.Names one but mixes up which is changed and which is measured.Names the one thing changed on purpose (lamp vs. window) and the one thing measured (seedling height), clearly and out loud.
Controlled variables (fair test)Changes factors without tracking their effects.Controls some conditions but overlooks a plausible confounder.Controls relevant conditions, identifies remaining variation or confounders, and explains how the design strengthens but does not guarantee a causal inference.
Control / comparison groupRuns only the test condition, with nothing to compare it to.Knows a comparison is needed but sets up one that is not a fair baseline.Defines an appropriate comparison group and explains its similarities, differences, and allocation; does not assume organisms are identical.
Replication & sample sizeTests one seedling once and calls it settled.Runs a couple of trials but too few to trust, or cannot say why more would help.Plans enough seedlings and repeats to tell a real effect from a fluke, and explains why the number matters.
Procedure clarityKeeps the plan in their head; written steps are vague or missing amounts.Writes steps but leaves out a measurement, timing, or detail a stranger would need.Writes a procedure clear and complete enough that another person could run the exact experiment without asking a question.
Integration (cross-domain)Makes no supported connection between the source and the science.Uses the source but needs help connecting evidence, writing, or limitations to the science.Independently connects History, Reading, and Writing using a cited source, appropriate evidence, a limitation, and a scientific explanation.
What “Mastery” requires
The student changes one variable, controls the rest, builds in a comparison and writes steps another could follow — unprompted.
What does not pass
Changing several things at once, or running only the test condition with nothing to compare against, is Developing — no result could point to a cause.
Grading it at home

The split between Proficient and Mastery is could this test actually prove a cause? One thing changed, everything else held, a real baseline to compare against. Ask: how do you know it was the light and not the water?

▲ Page 4 — Anchor exemplars
Controlled Experiment · Calibration
Anchor Exemplars — To Calibrate Your Ear
Anchors
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Read these before you grade. They show what Mastery and Developing actually sound like, plus the edge cases where you should coach rather than decide on the spot.

A fair test with a control

▶ Mastery
“The one thing I’m changing is light — lamp versus window — and I’m measuring how tall each seedling gets. Everything else stays the same. I’ll grow four under each so one weird plant can’t fool me, and keep a control on the counter.”
▶ Developing
“I’ll put one by the window and give it more water and better soil and see if it grows. Just the one plant.” (Several changes, no control.)

Integration — Semmelweis’s two wards

▶ Mastery
“Semmelweis's clinics and the handwashing intervention were not randomized identical groups. Dated rates supported a prevention hypothesis, but staffing and other differences require attention. My planned fair test must state its own controls and limitations.”
▶ Developing
“Semmelweis worked in a hospital.” (No link to the controlled comparison.)

Edge cases — coach, don’t fail

▶ No baseline
Runs only the window condition. Coach: what are you comparing it to? Add a control before deciding; not yet on the comparison criterion.
▶ One trial only
Tests a single seedling once. Coach why more samples matter — one plant can fool you. Close, fixable.
▲ Page 5 — Score sheet (clipboard)
Controlled Experiment · Score Sheet
Unit Score Sheet — One per student
Score Sheet
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Student: ______________________________________    Date: _______________    Guide: _________________________

Mastery criteria — circle one per row

#CriterionDecisionNotes
1Independent & dependent variablesDev / Prof / Mast
2Controlled variables (fair test)Dev / Prof / Mast
3Control / comparison groupDev / Prof / Mast
4Replication & sample sizeDev / Prof / Mast
5Procedure clarityDev / Prof / Mast
6Integration (cross-domain)Dev / Prof / Mast

Fair-test design — technique check

Used a token this session?

☐ No    ☐ Yes — for criterion: __________
Tokens left this term after this session (choose one): ☐ 3   ☐ 2   ☐ 1   ☐ None left

Dev = Developing · Prof = Proficient · Mast = Mastery · Unsure between two levels? Circle the lower one and note what a re-do would need.