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Evaluating lab work–let me count the ways

Posted by Melissa on February 5, 2009

Prompted by Chad’s lament over at Uncertain Principles about grading lab write-ups , I’ve been considering the various approaches used to evaluate student work in curricular physics labs. Ideally, during their time as a physics major, students will have their lab work evaluated in different ways both within a particular course and throughout the curriculum so that they can acquire and refine a variety of skills. I came up with a list of ten evaluation methods that I have seen employed, and I jotted down a few of the benefits and drawbacks that come to mind for each of these approaches.

1. Full lab write-up: This is the traditional lab write-up complete with abstract and the usual introduction, methods, results and discussion sections.

Students practice written communication skills.
Students get experience integrating quantitative analysis, visual representation of data, and conceptual understanding into a single written product.
If students continue in graduate school, this prepares them for academic science writing.

Formal lab write-ups are time consuming both for the student to write and the instructor to grade.
If serious problems occur in the lab or the results are ambiguous, writing up a particular lab can be frustrating for students.  (To avoid this, I sometimes let students choose which lab they will write up.)

2. Patchwork lab write-up: Any given week, students are asked to write one portion of what would be a full lab write-up for the lab that week. One week a student might write an abstract, another week the methods section, another week the discussion, etc.

Students practice written communication skills.
Students and instructors can focus on one portion of a lab write-up, and have a more in-depth discussion about the important aspects of this portion of a full write-up.
Patchwork lab write-ups are less time consuming for both students to write and instructors to grade than a full write-up.

Without the associated context of the whole write-up, students can find it difficult to write in an authentic manner the one section that is the focus any given week.
If a student has a significant conceptual gap in some aspect of the lab work, it is not always possible to determine that from one piece of a write-up.

3. Group lab write-up: This is a traditional lab write-up but instead of having each individual write up a lab, a lab group works together to produce a full write-up.

Group lab write-ups promote student interaction and peer instruction.
When it works well, this approach encourages collaboration and peer editing/revising.

When it doesn’t work well, the instructor gets a disjointed write-up that has been written by three different individuals who didn’t consult with each other. It isn’t a cohesive document or a collaborative experience for the students, and the instructor isn’t sure how much each student put into the write-up and how much they got out of the lab.

4. Memo: This works particularly well in introductory labs. Students are given a context for the lab activity, and then asked as a group to write a brief memo about their results for an audience that is appropriate based on the context given. The memo is written before the end of lab; the instructor reads the memo and asks the students questions based on the memo.

Students practice both oral and written communication.
Students are introduced to the idea of tailoring their writing to a particular genre/audience.

Because of the brief nature of both the written work and the questioning, this method of evaluation lacks the depth of engagement of some of the approaches.
Students can have difficulty adjusting appropriately for the audience/context given and the rest of the exercise suffers as a result.

5. Written questionnaire:
Instructor passes out a worksheet with questions that the students must answer and turn in at the end of lab along with the data that they have collected

This approach focuses student attention on a few key concepts/aspects of lab and effectively probes student understanding of those concepts.
These questionnaires demand less time of students and instructors than full write-ups.

This method of evaluation provides more limited practice with writing skills.
Students may hone in only on aspects of the lab related to the worksheet, and not invest themselves in the broader lab experience.

6. Oral presentation as a group:
Students present their work in a chalk talk and/or powerpoint talk with time for questioning by the instructor.

Students practice oral presentation skills and thinking on their feet.
Through questioning, instructors can probe student understanding deeply and provide immediate feedback to students.
Students work as a team.

The presentations can take up a significant amount of class time.
A misconception by one student is more likely to go undiscovered by the instructor.
The instructor must be particularly sensitive to issues of student confidence and group dynamics to ensure all students benefit from the experience.

7. Individual oral presentation: Same as above, but each student gives his or her own presentation.

This approach has many of the same benefits as the group presentation, but a student must take complete responsibility for a presentation.
The instructor gains a clear understanding of what a student does and does not understand, and can provide personalized feedback.

Individual presentations take up even more class time than group presentations.
This approach places a significant workload on the individual students.

8. Hallway talk:
Students walk the hallways with the instructor, informally describing what they did, what results they got, and answering questions from the instructor.

This approach allows for an easy back and forth discussion in a more comfortable setting than the formal oral presentation.
Students practice oral presentation skills in a different context.

Because of the informal nature, students don’t always invest as much time in thinking about how to present their results.
Students don’t get practice in the visual presentation of data in the same way that they do for an oral presentation or a formal write-up.

9. Lab notebook:
Students keep meaningful lab notebooks, complete with lab objectives, data collected, analysis, results, and discussion, and these are turned in weekly for evaluation by the lab instructor.

Students practice good habits of data collection and record keeping.
This approach keeps students’ minds turned on during the entire lab period, and prevents students from thoughtlessly collecting reams and reams of data to be presented later.
The instructor gets a unique perspective into students’ thinking about their work in a manner that isn’t possible with polished final products.

This approach doesn’t provide students with a summative experience for the lab.
For the instructor, lab notebooks can be tedious to grade.

10. Instructor choice presentation from lab notebook:
In order to facilitate students keeping good lab notebooks, towards the end of the term the instructor has students give an oral presentation on one of the labs from earlier in the term. The instructor picks the lab on the spot, and the student must give an impromptu presentation based on the notes that he or she has in the lab notebook. (It might be good to give students a trial run early in the term so they recognize whether or not they have sufficient notes in their notebook.)

Students practice oral communication skills and thinking on their feet
This approach provides students with a real motivation to keep good lab notes.

If students do not keep a clear lab notebook and are unable to provide an informed presentation, the instructor doesn’t get a good sense of students’ understanding of the physics.

What methods of evaluating labs do you favor? Why? What methods of evaluating labs did you appreciate most when you were a student? What else would you add to the lists above?


One Response to “Evaluating lab work–let me count the ways”

  1. […] of us who regularly teach intermediate and advanced lab classes. I’ve blogged before about alternatives to traditional lab write-ups and also about the difficulty of getting students to keep good lab […]

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