In the sciences, evidence comes largely from experimental results, or data.

Whether you’re writing about your own experimental research or using another researcher’s data to support your own argument, it’s important to understand how experimental results are used as evidence of scientific claims.

Scientists collect two kinds of data through their experiments:

• Quantitative data looks at issues of how many. How many cells died as a result of treating them with a particular chemical compound? How many registered Republicans live in New York City?
• Qualitative data looks at issues of value. How does a student feel about (or value) herself in class? How does a teacher feel about (or value) the state’s imposed curriculum? Why is there a tendency to teach (or value) the curriculum differently in working class v. upper middle class schools?

Different experimental protocols support collecting quantitative and qualitative data. Regardless, all scientists (from Biochemistry to Social Psychology) use the scientific method.

Scientific Method

The scientific process typically starts with an observation (often a problem to be solved) that leads to a question. The initial answer to this question is called a hypothesis. A hypothesis is an educated guess that can be tested. To solve one problem, several hypotheses may be proposed.

Once the hypothesis is formed, it’s time to test it. Scientists design experiments to test the hypothesis in a laboratory or naturalistic (real-world) setting. Each experiment will have one or more variables and one or more controls. A variable is any part of the experiment that can vary or change during the experiment. The control group contains every feature of the experimental group except it is not given the manipulation that is hypothesized. A significant result passes a statistical analysis that demonstrates that there is less than a certain probability (usually 5%) that the result observed is from random chance.

Watch this video for an explanation of the scientific method, and how evidence is used in scientific writing.

In your previous science writing experience, you may have come across the Claim, Evidence, Reasoning (CER) framework. According to the CER model:

1. The researcher starts with a question
2. Gathers evidence to answer the question through experiments
3. Forms a claim based on the evidence
4. Explains the connection between the evidence and claim through reasoning. This reasoning should be grounded in established scientific definitions and principles.

This framework is useful for our purposes because it shows how similar science writing is to the other writing processes we’ve been looking at. We start with a question, gather evidence about this question through research, and then use reasoning to connect the evidence to a claim.

Do Newer Experimental Results Replace Older Ones?

People tend to think that newer is better with everything. Sometimes this is true: new phones are better than old phones and new textbooks are often more up-to-date than old textbooks. But the understanding many students have about scholarly articles is that the newer studies “replace” the older studies. You see this assumption in the headline: “It’s Official: European Scientific Journal Concludes…”

In general, that’s not how science works. In science, multiple conflicting studies come in over long periods of time, each one a drop in the bucket of the claim it supports. Over time, the weight of the evidence ends up on one side or another. Depending on the quality of the new research, some drops are bigger than others (some much bigger), but overall it is an incremental process.

As such, studies that are consistent with previous research are often more trustworthy than those that have surprising or unexpected results. This runs counter to the narrative promoted by the press: “news,” after all, favors what is new and different. The unfortunate effect of the press’s presentation of science (and in particular science around popular issues such as health) is that they would rather not give a sense of the slow accumulation of evidence for each side of an issue. Their narrative often presents a world where last month’s findings are “overturned” by this month’s findings, which are then, in turn, “overturned” back to the original finding a month from now. This whiplash presentation “Chocolate is good for you! Chocolate is bad for you!” undermines the public’s faith in science. But the whiplash is not from science: it is a product of the inappropriate presentation from the press.

When writing about experimental results, your job is not to resolve debates based on new evidence, but to accurately summarize the state of research and the consensus of experts in a given area, taking into account majority and significant minority views.