Using Model-Evidence Link Diagrams to Weigh Alternative Models in Argumentation - Introduction and Instruction Scaffold

Oct 26, 2026

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Explains how model-evidence link (MEL) diagrams function as an instructional scaffold for helping students critically evaluate scientific arguments. Frames critical evaluation and argumentation as core scientific practices focused on judging relationships between evidence and alternative explanations. Describes the MEL diagram structure, arrow types representing support, strong support, contradiction, and irrelevance, and a ranking pre-task that teaches falsifiability and changes in plausibility judgments. Includes student directions and sample evidence items illustrating how evidence connects to models and alternatives.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages6

Reading Time15 min

AccessFree to download

Critical evaluation and argumentation as scientific practices

The model-evidence link diagram

Diagram structure and arrow meanings

Ranking pre-task and falsifiability

Student directions and example evidence

Using model-evidence link diagrams to weigh alternative models in argumentation ~~ ~~ Doug Lombardi, Bret Sibley, and Kristoffer Carroll ~~ ~~ knowledge and weigh alternative explanations. Regret~~ ~~tably, high school graduates often aren’t critically evaluative about scientific topics. To help remedy that, this article presents an instruction scaffold ~~ ~~ called a modelevidence link (MEL) diagram ~~ ~~ designed to promote students’ ability to critically evaluate scientific arguments and deepen their understanding of fundamental science concepts. First, however, we discuss the role of critical evaluation in promoting argumentation in the science classroom. Critical evaluation and argumentation as scientific practices A Framework forK–12 Science Education (NRC 2012) explains how scientific and engineering understanding develops through multiple approaches used to investigate, model, and explain the world. A fundamental practice of scientists and engineers is coordinating evidence, models, and theories. This coordination occurs through critical evaluation, which involves making judgments about the relationship between evidence and alternative explanations of a particular phenomenon (McNeill et al. 2006) . The Framework places evaluation at the intersection of (a) investigating and (b) developing explanationsand solutions (NRC 2012, p. 45) . The Framework also states that evaluation requires critical thinking,“whether in developing and refining an idea~~…~~ or in conducting an investigation. The dominant activities in [evaluation] are argumentation and critique, which often lead to further experiments and observations or to changes in proposed models, explanations, or designs”(NRC 2012, p. 46) . Therefore, in science education, critical evaluation is simply the analysis of how evidence supports not only a hypothesis, model, or theory but also how evidence supports (or refutes) alternative explanations. The selected evidence may support more than one explanation in much the same way a prosecutor and defense attorney in a courtroom, for example, could use the same evidence to support opposing claims. The goal is getting students to critically evaluate the relationships among evidence and claims and to effectively argue about connections between evidence and models. We believe the model-evidence link diagram provides an instructional scaffold to meet that goal. 50 The Science Teacher The model-evidence link diagram As shown in Figure 1, the MEL diagram helps students evaluate and argue about the connections between evidencesand alternative models (Lombardi, Sinatra, and Nussbaum 2013; Chinn and Buckland 2012) . The structure and mode of MEL diagrams were originally developed by researchers at Rutgers University under the NSF-supported PRACCIS (Promoting Reasoning and Conceptual Change in Science) project (Chinn and Buckland 2012). Using a MEL diagram, students draw arrows in different shapes to indicate the varying relationships between each piece of evidence and each model. Straight arrows indicate that evidence supports the model, squiggly arrows that evidence strongly supports the model, straight arrows with an “X” through the middle that evidence contradicts the model, and dashed arrows that evidence has nothing to do with the model. But how do students learn more about the evidencesand develop the skill to weigh the connection between evidence and models? Students gain knowledge from readily available instructional materials (e.g., classroom activities, textbooks, or online resources) and can also use any data gathered through their experimentation or other activities. Then they use a quick ranking pre-task to better understand how scientists judge the connection between evidence and models (Figure 2, p. 52) . In this pre-task, students rank the importance of each arrow weight. Then they learn about the tentative nature of scientific information through a discussion of falsifiability (the ability for a

FAQs

What is the purpose of a model-evidence link (MEL) diagram?

It helps students evaluate and argue about how evidence connects to alternative models, strengthening their ability to critically judge scientific arguments.

How do students represent relationships in an MEL diagram?

Students draw different arrow shapes: straight arrows for support, squiggly arrows for strong support, straight arrows with an X for contradiction, and dashed arrows for evidence unrelated to the model.

How does the ranking pre-task support students’ understanding?

Students rank the importance of arrow weights, discuss falsifiability and contradictory evidence, and then re-rank to see that contradictory evidence often carries the greatest weight in changing judgments.

Oct 26, 2026

Upload by Connor