Claims, Evidence, and Reasoning (CER)

When a scientist explains something, it is important to see how they provide evidence and reasoning to support their claims.

Here is an excerpt that will help you understand the structure of scientific explanations using CER.  You should follow the same structure for all of your writing in this class - without evidence and reasoning for your claims, you are not demonstrating a very deep understanding.  

The Claims that you make in this class, need to take the form of an explanation (i.e. they must not simply be an observation).

A scientific explanation is a written or oral response to a question that requires students to analyze data and interpret that data with regard to scientific knowledge. Our explanation framework includes three components: claim, evidence, and reasoning. Our ultimate goal is to create a cohesive argument in which all components are linked together. 


The claim is a testable statement or conclusion that answers the original question. The claim is the simplest part of an argument and often the part students find the easiest to include as well as to identify when they are critiquing other peoples’ arguments. One of the purposes in focusing on scientific arguments is to help students include more than a claim in their writing.

The evidence is scientific data that supports the student’s claim. The data needs to be both appropriate and sufficient to support the claim. A good argument only uses data that supports the claim in answer to the original question. Students should also consider whether or not they have sufficient data. When students are selecting their data to use as evidence, they should consider both whether it is appropriate to support their claim and whether they have enough data to support their claim. 

Reasoning is a justification that shows why the data counts as evidence to support the claim and includes appropriate scientific principles. The reasoning ties in the scientific background knowledge or scientific theory that justifies making the claim and choosing the appropriate evidence. Often students simply make a general link between the claim and evidence. You want to make sure to include the scientific background knowledge that allowed you to make that connection between claim and evidence.

From Katherine L. McNeill, Boston College and Joseph Krajcik, University of Michigan.

Below I have attached the General CER Sheet that we used in class to develop our first CER statements.

Mike Todd,
Dec 17, 2012, 6:31 AM