In the Classroom
Peer-Evaluated Poster Sessions: An Alternative Method to Grading General Chemistry Laboratory Work Todd Wimpfheimer Department of Chemistry and Physics, Salem State College, Salem, MA 01970;
[email protected] Laboratory work in a general chemistry course is usually evaluated using traditional methods such as fill-in-theblank data sheets, laboratory notebooks, and formally written lab reports. These methods are time-honored but may not be the only way to assess laboratory performance. An alternative assessment technique, the poster presentation, has already been used in the lecture for poster exams (1) and as a singular project (2–4). Posters have also been used in the laboratory but usually as a onetime project (5). In all the preceding cases the student posters were graded by faculty members or a group of faculty members. This article reports the use of weekly peer-evaluated poster sessions as a method for evaluating laboratory work in a general chemistry lab. Traditional Methods of Evaluation Students have traditionally been evaluated in general chemistry laboratory by either handing in a completed data worksheet, having their lab notebooks graded, or by writing a formal lab report. The worksheet is often set up so the student can fill in the blanks with their data. Often the units of the measurements are already provided. These worksheets are usually used with what are often called “cookbook” laboratories. Students follow the “recipe”, fill in the blanks on the report sheet, and hand in the results at the end of the laboratory period. The report sheet often resembles a tax form, where students are asked to subtract line 5 from line 4 and put the answer on line 6. While there are advantages to this worksheet approach, such as ease of grading, these worksheets do not demand much conceptual understanding on the student’s part. Laboratory notebooks are sometimes used as the basis for assessing lab work. Careful checking does teach the student the value of recording all data and observations in the notebooks. Lab notebooks are often graded using a pass–fail system and are sometimes used in conjunction with laboratory reports. The formal laboratory report is a common instrument for evaluating laboratory performance. This is usually in the form of a technical article with sections like introduction, materials and methods, data, results, and conclusions. Despite detailed instructions to the contrary, students often tend to focus too much on unnecessary procedural detail and not enough on the meaning of their results. While it is true that the student gains experience in technical writing, the learning of chemistry concepts may not be enhanced by the preparation of formal lab reports as much as the instructors would like to think. Technical writing experience is helpful for students as they will probably be writing scientific articles in the future. The chemistry students at Salem State, however, are often asked to present a poster before they are asked to write a jour-
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nal article. Our students, like many undergraduate students, present posters at college events, regional conferences, and American Chemical Society meetings. It is important, therefore, to give students experience in the presentation of research and other information via a poster presentation because they will likely do that before they write a technical article. Evaluation via Posters There are many benefits to the presentation of lab work using posters. The poster encourages creativity and gives another form of assessment that can take into account this creativity. Felder has noted that different techniques should be used so as to reach a student body with varied learning styles (6). Posters also, perhaps owing to their discrete size, stress the clear and concise presentation of information. They can also encourage collaborative work in a way that writing a lab report cannot. Finally, and not unimportantly, students (and the instructor) have a positive attitude towards them. Students find preparing a poster much more enjoyable than writing a lab report. Rarely has a student in my class been heard to remark that they are proud of the lab report they just handed in. I regularly hear students tell me and other students how proud they are of their poster. The student posters are currently graded via peer review by the other students. The process of peer review enhances the students’ ownership of the material. They feel much more connected when they are asked to be a “specialist” and grade the posters of their colleagues. This also gives the students the opportunity to be exposed to many examples of data handling and interpretation. These iterations help the calculations “sink in”. Student-active methods such as peer-review shift the responsibility of learning more towards the student (7). Poster sessions are logistically feasible with the small laboratory sections that many instructors teach. Owing to safety reasons, enrollment in laboratory sections are usually held to under 20 students, a small number that can easily perform the required grading and a new experiment in a single period. Execution At Salem State the CHE 231 Quantitative General Chemistry course is a fourth-semester chemistry course taken by almost exclusively chemistry and biology majors. Enrollment in the course over the past three semesters has been between 6–18 students with the lab sections being limited to fewer than 15 students. Over the past year and a half in the laboratory for this course, all the lab work has been evaluated by peer-evaluated poster presentations. Each week the students perform an experiment, handing in carbon copies of their lab notebook at the end of the period. The copies ensure that the data that were recorded are the same data that
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In the Classroom
appear on their poster. The students set up their posters at the beginning of the next week’s lab. A brief discussion of what to look for in the data handling and the range of accurate and precise answers is given to guide the student graders. Students are reminded to grade fairly based only on what appears in the poster. The posters are then peer-evaluated by the class. Each student grades each poster including his or her own. Self-evaluation is important and further increases students’ ownership of the material. The evaluation of the poster is done by filling out a grading sheet, which is handed out beforehand so that the presenters know the criteria upon which they will be graded. The grading sheet addresses both areas of form and content. Having each student grade several different sets of data strengthens students’ skills in data analysis. For a typical lab of 6–15 students, this grading usually takes 20–40 minutes of the three-hour lab period, depending upon the complexity of the experiment. After the grading is completed, the students then embark upon the next experiment. The grades given to each poster are averaged and that value accounts for 50% of the presenting grade. The instructor also grades each poster by filling out a grading sheet, which is identical to the students’ sheet except for an additional section that grades the students on their performance during the experimental portion of the lab. This is the sheet that will be returned to the students with their grade and comments. The instructor’s grade on the poster is worth the other 50% of the presenting grade and when combined with the peer-evaluated grade makes up 15 points of the total 25. A question where points were deducted by several peer reviewers is indicated in a comments column. This assessment is flexible and the weight of the peer-evaluation portion could be easily altered. Also, grading from other instructors or upper-class students could be included. After the total grade is compiled, students receive their grading sheets with feedback on their poster in time to better prepare their next poster. Currently the students are not required to orally present their poster. Since every poster is on the same experiment oral presentations could become a boring affair. Also students presenting later in the period would gain an unfair advantage after hearing several presentations on the same material. Even if as little as a couple of minutes were allotted for each student, oral presentations would require at least another half hour of lab time. After each student has seen and graded the results of all classmates, it becomes an easy matter to discuss pooled results. Time can be taken to discuss the results of the class as a whole and material can be presented on quizzes and exams. Assessment Having students present their lab results via peer-evaluated poster sessions can greatly enhance their laboratory experience. Many of the posters I have seen are magnificent. They are close in quality to posters displayed by faculty at ACS meetings. Formal lab reports, which have previously been written, were nowhere near the quality of a journal article.
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The posters appear to have helped the students better understand how to display information concisely. The tendency in written lab reports is for the student to recapitulate the procedure at length. There has been a noticeable decrease in calculation and mathematical errors. Apparently, pasting up their results in 24-point font makes the students check their work more thoroughly. Initial concerns over a student giving all good grades or all bad grades were allayed. There were differences in some of the more subjective questions on the grading sheet, but in general the grades given by the students paralleled those given by the instructor. Some thought has been given to penalizing student grades that vary greatly from the average but nothing has been implemented thus far. If a student wants it, the student’s poster is returned; otherwise, students sign a waiver allowing for the posters to be displayed around the department in the future. This helps incoming students see examples of quality posters and also beautifies the lab and lecture rooms. Student response has been positive. Student comments on an assessment questionnaire were usually along the lines of “...poster sessions help to break up the stress…” and “…The poster sessions were a good way to see what the data really looked like. I think they helped put each lab into perspective.” Some students commented that “…I also don’t like grading each other’s posters...”, but positive comments were in the majority. When asked to rank how much the poster presentations helped their learning on the following scale, 1 = no help, 2 = a little help, 3 = moderate help, 4 = much help, and 5 = very much help, the average over the year and a half was 3.73. In the fall 2002 semester when 14 students were assessed with the statement “I would rather present posters than write a formal laboratory report” on the same scale, the average was a 3.8 with no individual grade lower than a 3. Future statistics on more students will help to clarify these results, but for now these results seem encouraging. Finally, students enjoy creating posters. Although they may initially feel that they are “just” doing a poster, they do as much if not more work organizing and concisely presenting their findings than when they write a report. I also personally look forward to the poster sessions. Every week shows a creative side to the students that was never seen by reading lab reports. As these peer-evaluated poster sessions are continually refined, I find them to be an effective, alternative way of assessing laboratory work. Literature Cited 1. Mills, P.; Sweeney, W. V.; Marino, R.; Clarkson, S. J. Chem. Educ. 2000, 77, 1161. 2. Sisak, M. E. J. Chem. Educ. 1997, 74, 1065. 3. Dunstan, M.; Bassinger, P. J. Chem. Educ. 1997, 74, 1067. 4. Huddle, P. A. J. Chem. Educ. 2000, 77, 1154. 5. Kennedy, J. H. J. Chem. Educ. 1985, 62, 1104. 6. Felder, R. M. J. Chem. Educ. 1996, 73, 832. 7. For example: Kovac, J. J. Chem. Educ. 1999, 76, 120. Kovac, J. J. Chem. Educ. 2001, 78, 93. Farrell, J. J.; Moog, R. S.; Spencer, J. N. J. Chem. Educ. 1999, 76, 570.
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