An Introduction to Claim-Evidence-Reasoning (CER)  

An Introduction to Claim-Evidence-Reasoning (CER)


What exactly is CER, and how does it work?

CER all starts with a question asked by the teacher. This question is based on a phenomena or lab experience. The student’s explanation or answer, as you may have guessed, will consist of three parts: a claim, the evidence, and the student’s reasoning.



A claim is a statement that answers the question. It will usually only be one sentence in length. The claim does not include any explanation, reasoning, or evidence so it should not include any transition words such as “because.”



The evidence is the data used to support the claim. It can be either quantitative or qualitive depending on the question and/or lab. The evidence could even be a data table the student creates. Students should only use data within their evidence that directly supports the claim.



The reasoning is the explanation of “why and how” the evidence supports the claim. It should include an explanation of the underlying science concept that produced the evidence or data.




When I introduce how to write a CER response in a science classroom, I start with a non-science example. For students to be successful in writing a CER response, they must be able to make connections between their claim and evidence. If you start with something students are familiar with, they are more likely to fully understand what to write in each section. A non-science example I have used in the past is a Doritos commercial with the proposed question, “what happened to the cat?”




Utilize the template above to complete a CER based on the video. The driving question will be “What happened to the Cat?. 


CER Refinement

Argumentative reasoning is a skill that takes practice. This means that students will not write a perfect CER response their first attempt. They will need guidance and support from you, the teacher, as they write CER answers over labs conducted in class. It is useful for the teacher to model a sample CER response with the students in the beginning. However, students should first attempt to write their own CER response from the lab prior to the modeling. As you discuss with the class your sample CER response make sure you are emphasizing the concepts for a successful claim, evidence, and reasoning answer. Use the provided CER checklist to assist you with this discussion.


Students should use the CER Graphic Organizer resource as they continue to develop their writing skills and analyze their lab results. However, with continued use of CER their writing should become more refined and polished. Instead of the teacher modeling a sample response, students can now peer review answers and provide feedback to each other. At this point in your class, you have taught your students what it is truly like to think and write like a scientist!