Claim + Evidence + Reasoning = Explanation (CER)

12 min read
Claim + Evidence + Reasoning = Explanation (CER)

Writing a claim doesn’t have to be difficult, it’s your answer to a question that is asked along with your evidence and reasoning. For instance, if a friend asked you this question: “should my little brother get a cell phone?”. You might answer cell phones can be unhealthy for kids. Always remember not to start your claim with “I believe” or “I think”.

That’s a great arguable claim, but what evidence do you have to support it. You can make any claim you want, but if you can back it up with evidence, nobody will take you or your argument seriously. Evidence is reliable information that supports or backs up your claim. However, it is very important to cite the sources you use so others won’t think you just made it up and it can be verified as a reliable source.

To support your claim, according to research published in the journal of behavior addiction, overuse of smartphones is associated with various mental health concerns such as anxiety, depression, stress, and low self-esteem cited PA nova and Carbonyl 2018. Now you have your evidence to back up your claim. You need to connect the two with reasoning and tell how or why the evidence you have given supports your claim. For example, kids with smartphones all the time can lead to health problems.

Claim + Evidence + Reasoning = Explanation

So now let’s put let’s together, cell phones can be unhealthy for kids according to research published in the journal of behavior addiction, overuse of smartphones is associated with various mental health concerns such as anxiety, depression, stress, and low self-esteem cited PA nova and Carbonyl. Kids are on their smartphones all the time and the evidence proves that it can lead to major health issues. Now you know what it takes to write a strong claim.

What are Claim, Evidence, and Reasoning?

When a scientist makes a claim, he or she must explain it and have evidence to back it up. When you write like scientists, you need three different parts to complete your scientific argument. These three parts include, claim, evidence and reasoning.


The claim is what you think.


The evidence is the data that you see.


The reasoning is the science that you know that connects your evidence and your claim.

A claim is a statement that answers the question. The maximum length of writing a claim is just one single sentence. The claim does not include any explanation, any reasoning, or any evidence. So it should not be including any words like “because”. The evidence is the data used to support the plane, it can either be quantitative using numbers or qualitative using observations depending on the question or lack.

You should have at least three pieces of evidence that support your claim. Remember two pieces of evidence can be a coincidence, but three is a pattern. The reasoning is the explanation of why and how the evidence supports the claim. It should include an explanation of the underlying scientific concept that produces the evidence or data. When you are writing your reasoning, think of the scientific logic behind it and the science that you have learned and how it applies to your claim. This is the time for you to see and analyze the “because of” statements.

So after you have conducted the experiment and you have collected the data and you have collected your evidence, you are going to tell why does the evidence supports the claim.


How CER Works in A Science Classroom?

CER is a framework for making explanations in the science classroom. It’s a skill that teachers should give their students and students should have it to improve their scores on lab write-ups on essays or big exams. In science, you gather evidence through investigations of the natural world and then you come up with explanations that are critiqued over time. Unfortunately, a lot of time in a science classroom, the investigations are developed by the teacher itself, and the students are just going through a cookbook lab.

Therefore, it is important to avoid that and you also spend a lot of time on the investigation itself on the variables and controlling the variables, and then when you get to the end of coming up with an explanation of what you learned, you kind of fall down on that point. So the CER is a framework that makes this explanation making explicit.

This is an acronym, the C stands for the claim, the E stands for evidence, and the R stands for reasoning. Sometimes, you will hear a rebuttal added at the end of that, that’s looking at somebody else’s claim, evidence, and reasoning.

The claim is an answer to a question that’s asked, evidence is going to be what you gather empirical evidence that gathered, that’s gathered in the lab or through research, and then finally, the reasoning is going to be a logical connection between the evidence and the claim that you are trying to make. Now students will generally do very well at the evidence gathering but they fall when it comes to this logical connection. So a nice tip is to make sure that your reasoning is based on some kind of a scientific definition rule principle. That’s a way in science.

Now, what should a teacher provide? A teacher should simply provide a good question and a way to answer that question. Let’s say in the science classroom, a teacher gives students a bunch of dice, but they different-looking differentiate skew dice that look like this and the teacher asked them the following questions:

Are these skew dice fair? Start gathering the evidence right away.

Are these skew dice fair

They could roll the dice bunch of times they could measure the dice, look at their center of gravity or maybe measure all of the sides to make sure that they are all the same. But before jumping on the evidence part, you need to make sure that you have the question and you understand what’s being asked. Make sure that you could define everything that’s in this question itself.

Let’s go to the actual science question that we could answer is air matter. That’s a question you could answer in the science laboratory before we dig in and start gathering evidence. However, we should frame the question and make sure that we understand what every term means. So what is air? Air is an invisible substance that surrounds the earth. What is the matter? Matter is anything that takes mass and consumes much space, also it is composed of atoms. What else do you know about the matter, it can be neither created nor destroyed so sometimes it is helpful. In the beginning, to get all of these listed out so that we can use them at a later date.

Generally, you must start by gathering evidence. For example, you take a balloon, put it on a scale, and then you fill up a balloon and put it on the same scale. This shows that there is an increase in mass and then maybe you want to look at the takes up space side of the matter. Then maybe, you take a bottle filled with water pump air into it and you can displace some of that water and so now, you can make a claim that yes errors matter. That’s going to be your claim gathered evidence, but how do you do the reasoning.

Well, the reasoning is easier if it’s tied to one of those scientific definitions. So your reasoning could be, the mass of the balloon increased when the air was added indicating that the air has mass. The air displaced a volume of water indicating that air also has a volume since matter must have both mass and volume. However, the evidence suggests that errors matter that the reasoning part is what you hope your students will start to write and they never do.

Generally, when they are doing a lab write-up, they simply tell their teachers the evidence they gathered over and over. However, the teacher expects a connection between the evidence that you gathered and the explanation that you are trying to make. Now you could do a rebuttal on that, you could say well let’s look at the evidence here, you blew the balloon up so that’s air coming from your lungs and not from the environment, so that could impact. Maybe, it’s water there, and also it looks like there’s air right here. And so, you are measuring air and you measuring air pressure and so now, you can have argumentation or you can talk about the evidence or the reasoning.

Now all you do when you are doing labs that use claim evidence reasoning is just give them a good question and a material to answer the question you could give them a bunch of magnets and say which of these is the strongest. Or you can give them a bunch of paper clips, rulers and whatever and they have to answer this question. You need to make sure you frame the question and define everything inside it. What is a magnetic string and if you say it’s a measure of attractiveness or attractive force between a magnet and magnetic material? Do you know what a force is? Once you have all of these definitions, it will much easier for you to do any interaction.

One thing that confuses students a lot is when you boil water it gets to around 100 degrees Celsius and then it stays there. So again, students will gather a bunch of evidence whats some relevant evidence you can see is where a phase change from liquid to gas, we can see that it’s adding heat, but the temperature is not going up. So you can gather a bunch of evidence, but then making that connection, making the reasoning, is going to be based on some kind of a principle and you could try to make that connection. So CER is a way to make explanations and if you step through those three parts when you are asked to explain what you learned as long as you say here’s my claim, is the evidence, and here is the reasoning to back it up, you are going to do much better than you have in the past.

CER is a way to make explanations and if you step through those three parts

So this was all about the Claim, the Evidence, and the Reasoning (CER). We hope you are now much clear with the main concept of CER and how it can be used in a science classroom. Do let us know your feedback in the comment section below.