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March 19, 2021

What’s Your Evidence?: Teaching Students Scientific Explanations

Every day we are bombarded with claims about how to lose weight, stop smoking, become a better athlete, or make quick money. Yesterday, at the grocery store, I picked up a jar of peanut butter claiming: “Reduced Fat.” The uninformed consumer may think, great, I’ll buy this kind because it’s healthier. However, if you check out the food label on the back, you’ll see some other not-so-healthy differences between this product and the regular option: more sugar and salt!

Skippy labels

Food companies will often dilute a product with water to reduce the percentage of fat and then add salt and sugar to make up for the lack of flavor. When we consume excess sugar it gets converted by the liver into fatty acid—yup, that’s right, the extra sugar turns into fat! So, is the “low fat” option really a better choice? (Check out this 60 Minutes segment for more info on the adverse effects of sugar.)

Implications for the Science Classroom

To evaluate claims and make strong arguments of their own, students need to learn the features of a scientific writing. This blog describes the Claim-Evidence-Reasoning-Rebuttal  (C-E-R-R) framework for constructing scientific explanations and includes tools for teaching this approach to students, including scaffolding tips, a rubric, and examples of this approach in each of the sciences.

What is the C-E-R-R Approach?

This is an instructional approach designed to help students construct scientific explanations, by breaking them down into their component parts:

  • Claim: A statement or conclusion that answers the question asked or the problem posed.
  • Evidence: Scientific data that supports the claim.  The data needs to be appropriate and sufficient to support the claim.
  • Reasoning: A justification that connects the evidence to the claim.  It shows why data counts as evidence (as data, without interpretation, is meaningless) by using appropriate and sufficient scientific principles.
  • Rebuttal: Recognizes and describes alternative explanations, and provides counter evidence and reasoning for why the alternative explanation is not appropriate.

Examples of the C-E-R-R Approach in Each of the Sciences (click on the image to download the document):

examples of c-e-r-r 2

How can I support students to construct robust explanations?

1) Explicitly introduce the C-E-R-R framework so students know the components of a scientific explanation.

2) Model how to write explanations

3) Use this rubric to clearly communicate expectations for students’ explanations

3) Project and discuss strong and weak examples of explanations

4) Provide students with sentence stems:

  • Claim:
    • – “In response to the question posed, I believe that…”
  • Evidence (i.e., facts, observations, measurements, statistics):
    • – “I observed that…” “I measured…” “According to the video/reading…”
  • Reasoning:
    • [See examples above of C-E-R-R in each of the sciences]
  • Rebuttal:
    • – “Some might argue that…[state opposing argument]…However, due to…[provide counter evidence]…this is not an appropriate explanation.”

5) Use these productive talk prompts for teachers:

  • Asking for Evidence or Reasoning:
    • – “Why do you think that?” “What’s your evidence?” How did you arrive at that conclusion?”
  • Challenge/Counterexample:
    • – “Does it always work that way?” “How does that idea square with you classmate’s example?” “What if it had been a copper cube instead of an aluminum cube?”
  • Agree/Disagree:
    • – “Do you agree/disagree? (And why?)” “What do you think about what your classmate said?” “Does anyone want to respond to that idea?”

6) Have students draw a model, label it, and then explain the phenomenon using the C-E-R-R approach (see the example below):

Final Explanation - C-E-R - Model Checklist

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