Same Writing › Answering questions › Claim, Evidence, Reasoning (CER)
What is Claim, Evidence, Reasoning?
CER is a three-part formula for explaining something with proof: make a Claim that answers the question, give Evidence (data, observations or facts), and explain your Reasoning: the science idea that connects the evidence to the claim. It's most common in science class.
- Claim: one sentence that answers the question.
- Evidence: numbers or observations, not opinions.
- Reasoning: the rule or idea that explains why the evidence proves it.
Why schools teach it
It's how scientists argue
Science standards ask kids to argue from evidence (NGSS Science and Engineering Practice 7), and middle school writing standards ask for claims backed by relevant data in science and social studies (WHST.6-8.1). CER is the format most teachers use.
The reasoning step is what separates CER from just listing results. It asks “why does this evidence prove your claim?”, which is where the science learning shows.
At the kitchen table
What to say, and what to skip
Say this
What's your answer in one sentence?
ClaimWhich numbers or observations support it?
EvidenceWhat science idea explains why?
ReasoningWould someone who disagrees be convinced?
Skip this
- “I think” or “I feel” in the claim.A claim states the answer plainly.
- Evidence without numbers when there's data.Use the actual measurements.
- Repeating the evidence as the reasoning.Reasoning explains why, using a science idea.
See it in action
Do plants need light to grow?
Claim
Plants need light to grow well.Evidence
In two weeks, the plant in sunlight grew 9 cm and the plant in the dark grew 2 cm.Reasoning
Plants use light to make their own food (photosynthesis), so without light they cannot get the energy to grow.
In middle school, CER often adds a rebuttal: why another explanation doesn't fit.
Free practice sheet
Make a CER sheet
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Parents also ask
Is CER only for science?
No. Social studies uses it with sources as evidence, and some English classes use it too.
What counts as evidence?
Data, measurements, observations or facts from a source. Not guesses or opinions.
What's the hardest part?
Reasoning. Ask “what rule or idea makes this evidence prove the claim?”
What's CERR?
Claim, Evidence, Reasoning, Rebuttal: answering what someone who disagrees might say.