Evidence Strength Hierarchy

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About This MicroSim

This interactive MicroSim helps students explore the concept. It supports the learning objectives in Chapter: Evidence and Justification.

How to Use

Use the interactive controls below the drawing area to explore the visualization. Hover over elements for additional information and click to see detailed descriptions.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://dmccreary.github.io/theory-of-knowledge/sims/evidence-strength-hierarchy/main.html"
        height="450px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Grade Level

9-12 (High School / IB TOK)

Duration

15-20 minutes

Prerequisites

• Familiarity with the concept of "evidence" and why it matters in knowledge claims
• Basic understanding of the scientific method (hypothesis, experiment, conclusion)
• Awareness that different types of evidence carry different persuasive weight

Learning Objectives

• Evaluate the relative strength of different evidence types (e.g., anecdote, case study, RCT, systematic review) and assess how contextual factors alter evidential weight

Activities

1. Exploration (5 min): Open the sim and observe the default evidence pyramid. Read the labels on each tier from bottom (weakest) to top (strongest). Note which evidence types you recognize from science classes versus everyday life. Hover over each tier to read its description.
2. Guided Practice (10 min): Adjust the contextual sliders (sample size, number of replications, level of expertise) one at a time. After each adjustment, observe how the pyramid reorders. Record at least two examples where increasing sample size elevated a lower-tier evidence type above a higher-tier one. Discuss with a partner: Why might a well-designed observational study with 100,000 participants outweigh a small randomized controlled trial?
3. Assessment (5 min): Without using the sim, rank the following from weakest to strongest evidence for the claim "Exercise reduces anxiety": a personal testimonial, a meta-analysis of 30 RCTs, a single case study, and an expert opinion editorial. Then check your ranking against the sim with default settings. Explain any differences.

Assessment

• Accurately ranks at least five evidence types from weakest to strongest in a default context
• Provides a clear written explanation of how at least one contextual factor (sample size, replication, or expertise) can shift the relative weight of evidence types
• Connects evidence hierarchy concepts to a real-world TOK knowledge question

Quiz

Test your understanding with this review question.

1. A single randomized controlled trial (RCT) with 50 participants finds that a new drug reduces headaches. A large observational study with 500,000 participants finds the same result. Which statement best reflects how context affects evidential weight?

1. The RCT is always stronger because randomization eliminates all bias.
2. The observational study is always stronger because it has more participants.
3. The relative strength depends on contextual factors such as sample size, study design, and potential confounders.
4. Both are equally strong because they reached the same conclusion.

Show Answer

The correct answer is C. While RCTs are generally ranked higher than observational studies due to randomization, contextual factors like sample size, effect size, and confounders can shift the relative evidential weight. A well-controlled observational study with half a million participants may provide more reliable evidence than a small RCT with limited statistical power.

Concept Tested: Contextual factors in evidence evaluation

References

1. Greenhalgh, T. (2019). How to Read a Paper: The Basics of Evidence-Based Medicine and Healthcare. Wiley-Blackwell.
2. Guyatt, G. et al. (2008). "GRADE: An Emerging Consensus on Rating Quality of Evidence." BMJ, 336(7650), 924-926.