Claim Evidence Reasoning in CER Writing

[Intro]

Claim, evidence, and reasoning is a scaffolding technique for construction of scientific explanations. This methodology was first presented in the context of science education by Katherine McNeil and Joseph Krajick in 2012. Since then, this approach has been adopted nationwide in science education. Importantly for our purposes, this approach can also be used to ensure that we as writers are writing thorough and clear explanations.  

Explanations are everywhere in CERs. Some content in a CER is strictly technical detail, but there are many areas that will require us as writers to construct explanations. In particular, we will need to construct explanations when we are describing and defending our measurable safety and performance outcomes that we will use to evaluate our device; explanations are necessary when writing the state of the art; and explanations are also necessary for a complete and thorough analysis.  

Breaking down Claim, Evidence, and Reasoning, we start with the claim, which in this case means the conclusion or the point that we’re trying to make. This be something like “rates of adverse events are acceptable”. Next we move onto the evidence – these are the facts, data, statistics that relate to the claim. An example of evidence might include the rates of certain adverse events observed for a procedure as well as the rates reported in a standard of care document. Finally the reasoning. The reasoning is the underlying principle that connects the evidence to the claim. In this case, the reasoning is that the standard of care document includes information on what is commonly accepted in medical practice; another piece of reasoning is that our observed rate is lower than the STANDARD ACCEPTABLE rate. Now, in our reasoning here, we don’t spell out each and every piece of reasoning, because we know in CER writing, that our readers, the notified bodies, will understand that role of the standard of care document.  

Now that example was a little simple and might seem pretty obvious. But what happens when we dive into a more complex, and more realistic, example?

More often when writing a CER, we are dealing with multiple data and while we know what we would like our claim to be, we need to assess what claims the evidence supports and what reasoning is needed to fully explain the data and the claims. It can be very tempting to simply dump the table in our document and let the reader connect the dots. However, this opens up opportunities for misunderstanding and misinterpretation of the data. By using claim, evidence, and reasoning to construct our explanation, it decreases the likelihood of confusion and misunderstanding.  

So we have our table of evidence. To fully explain the data, we need to consider potential claims and what reasoning we can employ. Now certainly, we want to CLAIM that the procedural success rate is acceptably high, but we need to see if the evidence and reasoning support that claim. So we consider possible PRINCIPLES that we can use in our reasoning. The principles outlined here are not an exhaustive list, but they do represent a good starting point for our explanation.  

If we put it all together, we can have our claim “The procedure success rate is acceptable”. We support that claim with the evidence from the 4 studies; using reasoning to address and justify the lower rate from Study A, while also using the higher rates from studies B, C, and D to support the claim. Some of the reasoning is written out, specifically explaining that Study A is a lower level of evidence study than Studies B, C, and D. Additionally, we also include our reasoning that professional guideline data is a reliable source to determine if procedure success rates are acceptable. Note that in this example, there is some reasoning that may not be necessary to write out. For example, we could probably ASSUME that the reader will know that we want to place higher weight on higher level of evidence studies, and that lower level of evidence studies are less reliable when making claims. If we were not confident that our target audience will understand that reasoning, we should include the reasoning in our explanation.  

To summarize, we know that writing complete and clear explanations is necessary when writing a high quality CER. We can use claim, evidence, and reasoning to help us construct strong explanations. Finally, strong explanations will look differently depending on the target audience. It is important to know which reasoning principles your audience will be familiar with. When in doubt, it is a best practice to fully outline the reasoning you use when connecting your evidence to your claim. Doing this will reduce the likelihood of misunderstandings or confusion in your audience.