Clue 1: Orient yourself
Which tool measures length?
Use the labels and the picture's left-to-right, near-to-far, or before-and-after order. Name only what you can point to.
The question
Which tool measures length?
Why it matters: Clinical recommendations affect real children and families. Fair comparisons, bias control, ethical limits, and honest uncertainty keep a promising result from becoming a harmful claim. Today you practice the professional reasoning behind that work: The strongest design is the one that fits the question and controls its main threats.
On your WebXam
Ranking study designs by how much bias each controls
For life
To find the cause, change one thing and watch what changes.
Principle: Same look, different cause
Five principles we return to
Having it is not using it
Same instructions, different switches
Same look, different cause
Change one thing and watch
Boss or doorman?
Decides the result or only allows it
Held down, not gone
Remove the brake and it returns
Many roads, one ending
One result can begin many ways
Try the everyday version first
A tool wall has no single best tool for every job
A tool wall holds instruments built for different materials and measurements. The best tool depends on the question, not on which tool looks most advanced.
Do not jump to the biology yet. Treat the picture as a small system. Track its parts, follow one change at a time, and keep more than one explanation open until the picture supplies a way to separate them.
Clue 2: Trace one change
Which tool reveals a hidden structure?
Follow one object, stage, or path. Point to the first place where the situation changes instead of jumping to the ending.
Clue 3: Keep the cause open
Why would ranking every tool from weak to strong be misleading?
List more than one explanation that still fits. Name the extra observation that would help you separate those possibilities.
Now inspect the illustration
Work from the visible evidence. A useful answer names the part of the picture that supports it and leaves unknown causes open.
- 1Which tool measures length?
- 2Which tool reveals a hidden structure?
- 3Why would ranking every tool from weak to strong be misleading?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: Which tool measures length?
You can complete today's required check without opening the technical details below.
Ready for the real names? Optional tier 2
Technical rules and limits
Rule 1: Name the question type first.
Rule 2: Choose the design that can answer it ethically.
Rule 3: Identify the main bias or alternative explanation the design must control.
Where the analogy stops: Study designs involve people, biology, time, and uncertainty, not just tools with one fixed use.
Carry the previous idea forward
A falsifiable hypothesis links a defined change to a defined outcome and states what would count against it.
Today's technical takeaway
The strongest design is the one that fits the question and controls its main threats.
Now map the same rules onto biology
Match four cleft questions to four study designs
Ruler
Measurement or prognosis design
Randomized lane
Assignable treatment comparison
Microscope
Mechanism experiment
Educational illustration, not a clinical photograph or a patient-specific study plan. Use the supplied evidence cards and claim ceiling.
Mateo's case file: evidence supplied in this lesson
EXP03-E1
Repair timing is an assignable clinical choice when both options are acceptable.
Why it matters: A randomized trial can compare the treatment options under equipoise.
EXP03-E2
A suspected harmful pregnancy exposure cannot be assigned.
Why it matters: An observational design is required for that cause question.
EXP03-E3
A gene mechanism requires perturbation and molecular or tissue outcomes.
Why it matters: A bench experiment answers a different question than a treatment trial.
Make the clinical decision
You are chairing the design-selection meeting.
A teammate declares that an RCT is always the best design for every cleft question.
AMatch each design to the treatment, harm, prognosis, or mechanism question.
BUse an RCT even when it assigns suspected harm.
CUse a case report for every question because it is fastest.
Choose the design rule and match the three supplied questions to appropriate designs.
Evidence required
EXP03-E1 + EXP03-E2 Claim ceiling
You may select a design family. You may not call any design free of bias or automatically decisive.Go deeper Optional tier 3
Everything required for today is above. Open these only if you want the explainer, source trail, or download files.
The everyday model and Tier 1 check are the complete required path for this lesson.
Use these checks to keep your place. They are not turned in through the portal.
Check off as you finish
- Worked through the everyday picture and answered its three questions.
- Completed the Tier 1 check in plain words.
Turn in: Experimental Design lesson 3: Why We Trust Some Studies More Than Others
Go to Schoology to turn this in.
Submit one PDF. Put your first and last name in the document header. Name the file: FirstName LastName - Assignment Title - YYYY-MM-DD.pdf.
Open Schoology PDF upload helpIf you cannot get in, see Mr. Mendoza. Do not skip the work.
Optional legacy technical materials Open only if you want the original notes, vocabulary, artifact, and CER work
Before this page, you should know
- A hypothesis is a testable, predicted answer to a , and it must be falsifiable (some result could prove it wrong).
- The is what the researcher changes; the is what is measured; controlled variables are held the same across groups.
If not, review
Today's new idea is only
The ranks designs by how well each defends against bias, and a randomized trial tops it for treatment questions.
Goal: Students will rank common study designs in the and justify the ranking by how much bias each design controls, for both treatment questions and cause questions.
Know by the end
- The () ranks designs from weaker to stronger by how well each controls bias, a feature that pushes a result away from the truth.
- A has no comparison group; an (case-control, cohort) watches groups without assigning the exposure and can be misled by confounding.
- A uses chance to assign treatment, making groups alike on average even on unmeasured factors; it is the strongest single-study design for a treatment question.
- A and meta-analysis tops the ladder for treatment questions, but for a cause you cannot randomize, the top realistic rung becomes a strong .
1
What the ladder defends against
Model start: An ranks designs by how well each controls bias, the predictable pushing of a result away from the truth.
- Studies can be ranked in an (): a ladder from weaker to stronger by how well each design defends against being fooled.
- The thing each rung defends against is ____ (bias), any feature of a study that pushes the result away from the truth in a predictable direction.
2
From weaker to stronger
- A ____ report (Card A) tells a story about one or a few patients with no comparison group; useful for raising a question, weak for answering one.
- An (Card B) watches groups without assigning exposure and can be misled by ____ (a hidden third variable) and recall. A (Card C) uses ____ (chance) to assign treatment, so the groups match on average. A (Card D) combines all the good studies and tops the ladder for treatment questions.
3
The one caution
- This ladder is for treatment-effect questions; for a cause question you usually cannot randomize, so the top realistic rung becomes a strong , not an RCT.
- The ladder is a guide, not a law: a sloppy RCT can be worse than a careful cohort, so you still read the actual methods.
Everything you need for today is on this page. These links are optional.
What to read
Read the short plain-language explanation written for this lesson. Plain-language explainer for this lesson
Why this source matters
This explanation gives you the background for today's idea without making you decode a research paper: The ranks designs by how well each defends against bias, and a randomized trial tops it for treatment questions.
Words to unlock first
evidence hierarchylevels of evidencerandomized controlled trialobservational studycase report
Reading moves
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Stop point
Stop after the final 'Use it now' section. The research citations are available separately for advanced readers.
Your output
Write one claim-evidence sentence: state the main idea, then name the example or evidence that supports it.
Where this fits
Tested on (Ohio WebXam)
Genetics of Disease · 072130
PLTW lesson
MI · Experimental Design domain · Evaluating evidence and the hierarchy of study designs
WebXam domain
Molecular and Genetic Technology
Evidence to produce
Rank the four cards from least to most trustworthy for the question does earlier palate repair reduce later speech problems, writing one sentence per card naming the single biggest reason it sits where it does, then name which card's design becomes impossible to run for a cause question and why.
Lab / skill
Biomedical Innovations (BI) · Principles of Biomedical Science (PBS)
Everything required for today's decision is already in the case file and plain-language explainer. The links below are original papers and database records for teachers and advanced readers, not assigned student reading.
- NEJM. Timing of Primary Surgery for Cleft Palate (TOPS), 2023.
- Gamble C, et al. 2023. Timing of Primary Surgery for Cleft Palate (TOPS trial). N Engl J Med. [PMID:37646677]
- Sabbagh HJ, et al. 2023. COVID-19 risk factors and orofacial clefts, five Arab countries: case-control study. BMC Oral Health. [PMID:37118740]
- Page MJ, et al. 2021. The PRISMA 2020 statement. BMJ. [PMID:33782057]
- Claim: A is more trustworthy than a single for a treatment question.
- Evidence: The RCT has ____ (random assignment of who gets the treatment), which the lacks; the case report has ____ comparison group.
- Reasoning: Random assignment makes the groups alike on average even on unmeasured factors, so it protects the result from ____ in a way a single uncontrolled story cannot.
How this is graded (rubric)
For: Rank the four cards from least to most trustworthy for the question does earlier palate repair reduce later speech problems, writing one sentence per card naming the single biggest reason it sits where it does, then name which card's design becomes impossible to run for a cause question and why.
| Criterion | Proficient | Developing | Beginning |
|---|---|---|---|
| Complete | Every required part of the artifact is present and filled in. | Most parts are present, but one is missing or left blank. | Several parts are missing. |
| Accurate | The science and data are correct and match the evidence. | Mostly correct, with a small factual slip. | Key science or data is wrong. |
| Scientific reasoning (CER) | States a claim, backs it with specific evidence, and explains the reasoning. | Has a claim and evidence, but the reasoning is thin or missing. | Gives an answer with no evidence or reasoning. |
| Professional communication | Clear, organized, and labeled the way a clinician or scientist would write it. | Readable but disorganized or missing labels. | Hard to follow. |
| Submitted | Turned in through the route named under Submit here and confirmed. | Turned in, but in the wrong place or unconfirmed. | Not turned in. |
How the model answer scores against this rubric
- CompleteProficient: Nothing is left blank: the model fills every part of "Rank the four cards from least to most trustworthy for the question does earlier palate repair reduce later speech problems, writing one sentence per card naming the single biggest reason it sits where it does, then name which card's design becomes impossible to run for a cause question and why.".
- AccurateProficient: Every number and claim matches the case evidence.
- Scientific reasoning (CER)Proficient: It names a claim, cites the specific evidence, and explains the reasoning, not just the answer.
- Professional communicationProficient: It is organized and labeled like a real chart note.
- SubmittedProficient: It would be attached to your class form or handed in, and confirmed.
What's next: A randomized trial sits near the top because we can assign who gets the treatment. But we could never assign a baby to a harmful chemical in the womb. So how does science study a cause it is forbidden to hand out?