Peer Review: Critically Evaluating Conclusions & Looking for Experimental Error
Lesson 9 of 9
Objective: Student groups will be able to identify instances of experimental error to determine if initial group conclusions are valid.
I teach this lesson as a follow-up to the Writing a Lab Report lesson but it could definitely work as a standalone lesson (if you have an example of a lab report) or as a follow-up to any experiment where your students produced a lab report.
The focus of the lesson is on having students critically evaluate the work of their peers. My hope is that students will take this opportunity to evaluate others more seriously than producing their own work, where they can sometimes be a little too easily content. Looking for someone else’s mistakes can really bring out the inner critic!
The standard for this lesson pretty much speaks for itself. Students will be tasked with reading someone else's work, evaluating their argument (in this case, a scientific conclusion), and identifying issues that remain unresolved.
To begin this lesson, I commend students for their work over the course of the lesson sequence where they designed and conducted an experiment and then wrote a lab report. I collect all lab reports if they hadn’t already been turned in.
I then ask if, in the case of real scientists, the lab report represents the end of the road (i.e., does their work now become part of generally accepted scientific knowledge). If students need prodding, I’ll ask them to check their notes from the Scientific Method lesson. However they arrive at it, students should come up with the reply that the results of an experiment and the conclusions based on them don’t really become part of the body of scientific knowledge without first being checked by other scientists. If they don’t mention the exact term “peer review”, I’ll mention it as I write it on the board and explain that it involves closely reading and, in some cases, replicating the experiment to verify the conclusions of the scientists that wrote the report.
I let the students know that they will soon get a chance to review another group’s work to see if they followed the scientific method and produced reliable results, or if their errors invalidated their conclusions. However, we will first need to talk about the types of experimental error that can occur and lead to inaccurate conclusions drawn from otherwise excellent research.
I ask students to take out their notebooks and prepare to take some short notes. I then present the Experimental Error powerpoint. After writing down the definition of experimental error and the four types of error, I show the example slides.
For each example slide, I ask for a student volunteer to read the example and then ask the class what type of error occurred. Since the examples are in the same order in which they wrote down the types of error from slide 3, this isn’t the tricky part. I then ask the students to quickly confer with their partner to come up with an explanation of why this example illustrates this type of error. I then ask volunteers to offer their explanation. I repeat this process and also ask students how the scientist in each example could fix the error.
Slide 4: The ornithologist with the ruler.
This is human error because the scientist made the correct measurement but wrote it down incorrectly, which lead to a faulty conclusion when he looked at his data later.
Fix: double check measurements in the field. Take pictures.
Slide 5: The ornithologist drops his scale.
This is instrument error because by dropping the scale, the calibration was thrown off and all measurements after this fact read less than they actually were.
Fix: carry something with a known weight (e.g., a quarter, a marble, an action figure) and use that to check your instrument’s calibration.
Slide 6: The strawberry grower (part 1)
This is design error because she had an additional variable: distance from the plants were growing from the light source.
Fix: Line all pots along the window so they all receive equal sunlight OR grow them under artificial lights.
Slide 7: The strawberry grower (part 2)
This is unavoidable error because of the natural genetic variation of strawberries. Some may grow larger or smaller than others regardless of the nutrients they receive.
Fix: Use a larger data set: grow hundreds of strawberry plants to reduce the statistical significance of chance genetic variation.
Please note that these “fixes” don’t represent the one right answer in each case… push your students to be creative and ask for multiple solutions (e.g., use cloned strawberry plants to reduce unavoidable error).
After the powerpoint concludes, I ask students if they’re ready to find the mistakes the other groups made. I like to remind them that science is cooperative, not competitive, while also casually mentioning that there have been many heated rivalries between teams of scientists in the past. Hopefully this gets them in the mood to review their peers’ work critically.
I first distribute the individual peer review sheet (one per student) and the group peer review sheet (one per group). It’s important that these groups be the same as the groups for the previous lesson sequence. I then distribute lab reports to groups (other than the group that did the report). Although the lab reports should include all data that the groups collected during the experiment, they may have additional video data stored on phones or digital cameras that they obviously did not turn in with the lab report. If such video data exists, have groups exchange it as well.
Mirroring the procedure for writing the report in the last lesson, I ask students to complete the individual peer review (of an individual lab report) first. After about 15 minutes of this, I let groups know that they should be finished with the individual reports and begin working on the group peer review (of the group lab report).
After another 15 minutes, I have groups return the lab reports and review sheets to the original groups.
Please Note: The peer review worksheets assume that the lab reports being reviewed included both individual and group sections. You may need to alter them to fit with a different lab report format if you are presenting this as a standalone lesson.
Once the groups receive the review of their work, I have them quickly complete a feedback form, with questions of whether or not they agree with their peers’ review of their work (please note: to save paper, I print this form on the back of the group peer review).
One of the most fun parts about this activity is that the reviewing group gets to make their final assessment to publish or not to publish the work of the group they review. This can lead to some lively conversations and disagreements which, although they can be a little rowdy, are a great way to engage high school students’ interest in the scientific method.
In the last five minutes of class, I ask for all work to be turned in (I still need to grade it at this point).
I then ask students to quickly discuss with their groups a response to the following question: does the process of peer review help make scientific knowledge more reliable?
This is a big question for such a short period of time, but I hope to at least introduce it into their thinking to realize that, despite the fact that criticism can be somewhat difficult to accept personally, it protects science from manipulation and insures that only repeatable, observable, empirical facts become part of the body of scientific knowledge.