Analyzing Real Historical Errors to Understand Experimental Design

This digital lesson teaches the scientific method by examining real historical cases in which scientists reached incorrect conclusions due to flawed procedures, missing controls, or invalid reasoning. Students analyze these mistakes using modern standards of experimental design and then redesign the experiments correctly.

Rather than memorizing steps of the scientific method, students learn why those steps matter by seeing what happens when they are ignored.

The lesson uses three well-known historical examples:
• John Needham and spontaneous generation
• Clever Hans and observer-expectancy bias
• Darwin’s hypothesis of blended heredity

These cases allow students to practice identifying:
• uncontrolled variables
• missing or inappropriate controls
• biased observation
• unsupported conclusions

What Students Do

Students review the basic structure of the scientific method and then work through guided analysis of each historical case study. For every experiment, they:

• identify the original claim
• examine the procedure
• locate specific flaws in the design
• evaluate the conclusion
• propose a revised experimental design

At the end of the lesson, students complete a choice-based research task in which they investigate an additional historical scientific error using a linked timeline of case studies.

Key Concepts Reinforced

• Scientific method and experimental design
• Controls and variables
• Evidence vs. conclusion
• Observer bias
• Cause-and-effect reasoning
• Claim–Evidence–Reasoning (CER) writing

Why Teachers Use This Lesson

• Makes the scientific method concrete and meaningful
• Shows how real experiments fail
• Builds critical evaluation skills
• Integrates science and history
• Supports CER and argumentation
• Works for guided instruction or independent learning
• Minimal prep required

Format

This resource is a fully editable digital Google Slides lesson with built-in student tasks.

Includes:
✔ Structured student analysis activities
✔ CER writing prompts
✔ Experiment redesign task
✔ Student-choice research extension
✔ Printable or digital student sheets
✔ Teacher answer key
✔ Exit ticket assessment

Best Fit For

• Middle school science
• High school biology or physical science
• Scientific method units
• Inquiry and CER practice
• Early-year skill building
• Sub plans
• Interdisciplinary science/ELA lessons

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Grade & Course Recommendations

Best fit:

• Grades 7–10

• Middle School Science

• High School Biology

• Introductory science/experimental design units

• STEM electives

Why:

• Reading load + CER writing = middle/high school ready

• Historical examples align well with both MS-LS1/LS3 foundations and HS-level CER rigor

Cross-Curricular Connections & Extensions

ELA

• Evaluating claims and evidence

• Reading informational texts (historical primary sources)

• CER structured writing

• Argument writing and revision

History of Science

• Enlightenment science

• Evolution of scientific thought

• Impact of communication failures (Darwin & Mendel)

Social Studies / Psychology

• Observer-expectancy effect (Clever Hans case)

• Cognitive bias in experimentation

Possible Extensions

• “Rewrite the experiment” challenge

• Students storyboard their own historical scientific misconception

• Mini-debate: “Which scientific mistake was the most influential?”

• Research paper comparing two scientific failures

• Create a PSA: “How to Avoid Bad Science”

Daily slide + literacy - based exit ticket included with purchase

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NGSS Standards (Middle & High School)

Middle School NGSS

MS-ETS1-3 – Evaluate a design based on evidence to determine strengths and weaknesses.
MS-LS1-1 – Conduct investigations using scientific inquiry principles.
MS-LS3-2 – Use models to describe why traits do/do not pass on (Weismann example).
MS-LS4-2 – Identify patterns in evolutionary evidence (Darwin vs Mendel context).

Science & Engineering Practices (SEPs):

• Analyzing and interpreting data

• Constructing explanations

• Engaging in argument from evidence

• Asking questions & defining problems

Crosscutting Concepts (CCCs):

• Cause & Effect – flawed variables lead to flawed results

• Patterns – inheritance patterns refute pangenesis

• Scientific Knowledge Assumes an Order & Consistency

• Influence of Science on Society & Society on Science

High School NGSS

HS-LS3-1 – Ask questions about hereditary mechanisms.
HS-LS3-2 – Make and defend claims using evidence about genetic inheritance.
HS-ETS1-3 – Evaluate complex experiments, identifying flaws in design.
HS-LS4-1 – Analyze historical evidence supporting modern biological theories.

High School SEPs:

• Developing and using models

• Constructing arguments from evidence

• Evaluating claims

• Critiquing experimental designs

High School CCCs:

• Stability & Change (why acquired characteristics fail)

• Systems & System Models (proper vs. flawed experiments)

• Empirical Evidence
  

Common Core Standards (MS & HS)

Middle School CCSS

CCSS.ELA-LITERACY.RST.6-8.1 – Cite evidence from informational texts.
CCSS.ELA-LITERACY.RST.6-8.8 – Distinguish among claims supported by evidence vs. speculation.
CCSS.ELA-LITERACY.WHST.6-8.1 – Write arguments focused on discipline-specific content.

High School CCSS

CCSS.ELA-LITERACY.RST.9-10.3 – Follow complex experimental procedures.
CCSS.ELA-LITERACY.RST.9-10.8 – Evaluate the validity of reasoning and the relevance of evidence.
CCSS.ELA-LITERACY.WHST.9-10.2 – Write explanatory texts within scientific topics.
CCSS.ELA-LITERACY.WHST.9-10.1 – Construct arguments using valid reasoning and evidence.