Development of Analytical and Reporting Skills in Quantitative Analysis

Jul 7, 1998 - The development of skills is aided by having the stu- dents go through a set of stepwise experiences: 1. Students learn the basics of ch...
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In the Classroom

Development of Analytical and Reporting Skills in Quantitative Analysis R. J. Eierman Department of Chemistry, University of Wisconsin–Eau Claire, Eau Claire, WI 54702

This article is a description of activities carried out in quantitative analysis that have as their goal helping students develop skills in analyzing numerical results of chemical measurements, drawing conclusions from them, and choosing what to include in a report. The activities are designed to provide students guidance with appropriate tools and then to give them the freedom and responsibility to choose what to do and how to do it. Once the students have been exposed to and have practiced with the correct methods for calculating results, performing statistical analyses, and drawing conclusions from them, it becomes their job to decide when and how to apply those methods to their own experimental results. It is important that students learn that the decisions are up to them and that they are accountable for what they decide to do (and not do) as well as how they do it. Several aspects of the course (student management teams, cooperative group work) are included to help students learn that they are responsible for their own success and that of the course as a whole. The development of skills is aided by having the students go through a set of stepwise experiences: 1. Students learn the basics of chemical measurement procedures and methods for data reduction and statistical analysis. Initial learning is done primarily in the lecture. 2. Students apply those concepts to self-collected experimental data in instructor-defined laboratory write-ups. Feedback is given on how well they carried out the specific instructions. 3. In subsequent experimental write-ups students decide what to report and how to report it, given general instructions and the identity of the audience for whom the report is written. Feedback is given on what they did and didn’t do and how successfully they did it. 4. Finally, students choose, design and carry out a special project. They decide what data reduction and statistical analysis to do and report their results and conclusions to other students, the instructor, and other faculty members in a poster session

Basic statistical methods are taught (confidence interval, comparison of means, screening bad data, linear regression, and propagation of error) and there is a roughly equal split between traditional wet chemical methods (gravimetric and acid/base and EDTA titrations) and instrumental methods (molecular and atomic absorption spectrometry and potentiometry). A typical class consists of 56 students split into two 28-student lab sections. About 150 students take the course each year. The lecture and lab are usually taught by the same faculty member. The laboratory consists of a fairly typical set of analyses (see Table 1). Procedures for the analyses are provided in an in-house laboratory manual. The procedures have been written in a format that follows the Association of Official Analytical Chemists (AOAC) standard method format (1). Students carry out the procedures working alone or in structured groups, analyzing samples that are provided or that they collect themselves. They work through the experiments at their own pace. Write-up instructions are provided as the first students begin an experiment; often, lab lectures on the chemistry and details of the methods are provided after all students have begun working on an experiment. Lab reports are collected a week after everyone finishes the experiment and are graded by the instructor. Course Elements In this section the activities that are done to carry out the experiences described above are explained. The item numbers correspond to the steps described earlier.

An Overview of the Quantitative Analysis Course Quantitative Analysis (Chem 213) is a 5-credit course with lecture (3 hours/week) and laboratory (6 hours/week) taken by second-semester freshmen, sophomores, juniors, and some seniors after completion of general chemistry and in some cases organic chemistry. The course has dual goals of helping students learn the fundamentals of chemical analysis and to review some basic chemical concepts (equilibrium, acid– base chemistry, and electrochemistry) within that context.

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1. The Basics of Chemical Measurements and Data Analysis The first several weeks of lecture are spent addressing basic wet chemical and instrumental analysis strategies, methods for identifying and quantifying experimental error (accuracy and precision), and statistical methods for data analysis (confidence interval, comparison of means, screening bad data, linear regression and propagation of error). This is done in a fairly traditional lecture mode with frequent inclass problem solving and homework assignments, following the first several chapters of the textbook (2). In laboratory students use the UWEC Chem 213 Lab Manual to carry out the lab experiments. For all experiments in the course students are not allowed to bring the lab manual into the lab, but must transfer the pertinent information into their lab notebook before doing the experiment (3). This forces students to screen the experiment and write out the steps they need to complete the procedure. Students are free to refer to the lab manual outside the lab at any time. The AOAC standard method format of the experiments makes this process relatively easy and most procedures are about two pages in length. Students are taught to use a spreadsheet (Lotus 1-2-3 for Windows) in laboratory during the first several weeks of the semester (4). Each lab section spends two 2-hour sessions during lab time in a computer lab where each student is seated at a computer. The first hour of each session is spent introducing students to spreadsheet operations and the second hour is spent by the students practicing the operations; the instructor is present to help with problems. Students utilize an in-house guide to the spreadsheet, which is an appendix in the lab manual, to learn the operations and recall them later. Students learn to enter different types of data, write equations using relative and absolute addressing, move and copy cells and ranges, use @ functions, make X Y graphs, do linear regression and graph the fitted line on the plot, and save and recall files from floppy disks. During the early part of the semester a student “board of directors” is established (5, 6). This group of four to six students meets once per week, with the instructor attending every other week, to discuss issues associated with the course and provide feedback and advice to the instructor. Students volunteer to join the board and are invited to raise any issues and suggestions for changes they wish. A record is kept of issues that are discussed. This board helps students recognize that they have significant control and responsibility for the success of the course. 2. Application of Concepts in Instructor-Defined Write-Ups The students apply the statistical methods learned in lecture along with the spreadsheet to analyze the data and report the results of the first five experiments, following detailed write-up instructions. They have occasion to utilize each of the statistical tests they have learned and are asked to draw conclusions from results for each experiment. In several experiments they are asked to use a spreadsheet for data analysis. In the two aspirin analysis experiments (Experiments 3 and 4 in Table 1) students work in groups of two. The groups are structured to give each student a defined role in the experiment and to encourage positive interdependence between 870

the students, a design that follows the work of John Walters (7 ). The following excerpt from a handout given to the students describes the group structure. The report for each experiment consists of an initial report including data analysis and experimental results submitted by the “technician” to the “manager” and a larger report submitted by the manager to the instructor that includes further data analysis, conclusions, and answers to questions about the method. The technician is graded on her/his report (including accuracy and precision of the results) and the manager is graded on the technician’s report (including any corrections the manager chooses to make to it) and her/his Project Manager. This person is in charge of the experiment. It will be the manager’s responsibility to understand the experimental procedure, make decisions about what needs to be done and when, and to communicate that information to the technician. The procedures are found in the lab manual and the manager’s job is to interpret the procedure and coordinate the activities. The manager must make use of the available resources to complete the analyses and acquire the necessary data. In addition the manager produces the written report in collaboration with the technician and is graded on that report. Technician. This person is in the employ of the manager and will carry out the procedures as indicated by the manager. Questions should be directed to the manager. The technician will contribute to the written report and will be graded on their contribution. Each student will play one role for the volumetric analysis and the other role for the spectrometric analysis. Three reports will be completed by each pair of students. Each manager will complete a written report for their particular experiment with help from the technician and a comparison report will be submitted by both students. The instructor will act as a consultant during the analyses. Any and all questions from the Manager will be accepted before the analysis starts. After the analysis begins, questions (other than simple procedural questions) will be accepted only with payment of one apple.

own report. The comparison report is done as a team and both students receive the same grade on it. This structure for these experiments gives the students experience working together toward a common goal and forces them to practice communication skills in a science context. There is individual accountability and a reward for working together effectively, both of which are needed for effective group work (8). Students are asked to use the spreadsheet and the manager is responsible for reviewing the work of the technician, so the group members naturally help one another gain skills. The defined roles and the instructor acting as a consultant encourage students to take ownership of the experiment execution, data analysis, and report. In each of the first five experiments students are given specific written instructions on what to include in the report and frequently hints on how to do the calculations. By the end of those experiments they have carried out each of the statistical tests learned in lecture at least once. However, they have not been asked to decide what to do and when.

3. Students Decide What To Do and What To Report In the next two experiments (Experiments 6 and 7 in Table 1) students work alone to analyze vitamin C tablets and mouthwash. They are given general guidelines for their reports and the audience for whom the report is written. They are then asked to decide what data and statistical analyses to

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use and what conclusions to draw. The write-up instructions for the vitamin C analysis are shown below. The instructor responds to students’ questions about the details of the data analysis, but not to questions about what should be done. The idea here is that students need to develop the ability and confidence to decide how to handle experimental results to permit them to make appropriate conclusions. Giving them responsibility for asking what questions must be answered in the report is a good way to help them learn to solve the problems posed by the experiment (9). Having them do two consecutive write-ups in this format makes it Write-Up Instructions for Iodometric Titration of Vitamin C In this write-up you will report on your analysis of over-the-counter vitamin C tablets. The purpose of the analysis is to determine if the vitamin C value reported on the label is correct. The audience is an interested pharmacist who will use the results to decide whether to sell this product. The two-page, single-sided report should be structured as follows: 1. Brief description of the procedure, illustrating your understanding of how the analytical technique works. 2. Raw data and data analysis including sample calculations. 3. Results and statistical analysis of results. 4. Conclusions based on the results. You decide what results and data analysis are necessary to report as well as what statistical analysis is needed. You will be evaluated both on what you report as well as how well you do the data analysis and write up the results. NOTE: The two-page limit is a strict one; any extra pages will be ignored.

possible to give them feedback on what they have done on the first write-up so they can make adjustments on the second. In the vitamin C experiment students were graded on their procedure description (explanation of back titration and identification of the role of each of the important reagents), raw data analysis (standardization calculations, calculation of vitamin C content), statistical analysis (average, mean, and statistical comparison with label value), and the conclusions (statement of advice for the pharmacist). Part of the grade was also based on how close they came to the “correct” value for the vitamin C content— in this case, a range around the class average that also included the label value. Students lost points if any of these components were missing or if they were done incorrectly. Write-up instructions for measurement of the fluoride content in mouthwash were similar to these. The grading load in the course is not appreciably changed by this shift in the write-up emphasis. For a group of 56 students it takes between 3 and 5 hours to grade the reports from an experiment.

4. The Special Project The final step in the process is to give students responsibility for the entire experimental process. A handout given to the students provides a summary of the special project (see below). Several aspects of the special project bear comment, as follows. Students’ choice of a project forces them to make some

decisions and do library research with a focus. Students must decide what they are interested in and commit to a project related to that interest. In doing this they must envision themselves as analytical scientists, which gives the exercise a difSpecial Project For the last several weeks of this semester you will work on an analytical experiment of your own choice. You can work alone or in a group of two and the scope of the project will vary with group size. The steps in this project are as follows: 1. Choose a chemical analysis to do including a sample and analyte and an experimental procedure. 2. Write and submit a proposal that will be reviewed and approved by the instructor. 3. Collect the sample(s), carry out the analysis and the appropriate calculations and statistical tests on the data. 4. Present your project in a poster session during lab the last week of the semester. A summary of each of the steps follows. 1. Choice of Project Choose a chemical analysis that is of interest to you. Your interest may be due to any aspect of your life including your job, where you live, what your career aspirations are, etc. Consult with the instructor if you need some help in making this decision. The project will consist of a chemical analysis and should follow a procedure from a standard methods book or other reference. Methods can be found in McIntyre Library by searching the keywords, “standard methods”, “official methods” and “analytical methods” on the NOTIS system. Please bring any checked-out methods books to lab so others can utilize them, too. The scope of the project will vary with group size as follows: One person—Chemical analysis of sample. Two persons—Chemical analysis and investigation of some aspect of the procedure. This might be investigation of how varying an experimental parameter (e.g. temperature or pH) impacts the result. Again, consult your instructor if you need suggestions for this study. 2. The Proposal A one-page proposal will be submitted to the your instructor for review and approval. The proposal should include the following: 1. Statement of the objective of the proposal, i.e. what question will be answered? 2. Brief outline of the steps in the analysis. 3. A list of all reagents and equipment needed to carry out the analysis. The proposal is due to the instructor no later than 10 AM on Friday, November 15. 3. The Project Carry out the project in lab. Be aware that there may be scheduling problems associated with use of single instruments like the atomic absorption spectrometer. Plan ahead. Projects must be finished by the end of the day, Thursday, December 5. 4. The Poster Presentation The last days of lab (Wednesday and Thursday, December 11 and 12) will be spent presenting the projects and their results in a poster format. You will prepare a poster (at least 2’ by 3’) with text in large print that includes: a) Title, objective and name(s). b) Description of method. c) Data and results. d) Figures and graphs. e) Conclusions and discussion of results. f) References. On the day of the poster presentations, you will stand by your poster and answer questions posed by people viewing the posters. Students will take turns presenting their posters and visiting the posters of fellow students. Your project and poster will be evaluated by the instructor following a format sheet. You will be provided information on the grading process soon.

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ferent aspect from the previous defined experiments. Also note that if students choose to work with a partner, the scope of their experiment must expand to include an investigation of some aspect of the analytical procedure. This forces them to consider the factors that might influence the results of the experiment and design an experiment to test one of those factors (10). Submission of the proposal demands that students decide on their project and plan their experiment ahead of time. In addition they must identify chemical reagents and equipment needed to do the analysis and produce a summary of the procedure. This permits the instructor to provide feedback on the scope of the projects and to advise students about the probability of success, which reduces the number of projects that are too simple or too complex before they start. Some projects are rejected during the proposal process— usually before the formal proposal is written. Rejection is always accompanied by plenty of suggestions for alternative projects that are more viable. The laboratory is a busy place while the projects are being carried out. In a typical recent semester, 45 students completed 38 projects (7 pairs of students were formed) and 30 different analytical procedures were carried out. The largest challenges that students face involve understanding their procedures and adapting them to the specific samples that they are analyzing. Students learn by experience that the more you know about the composition of the sample, the easier it is to proceed with the analysis. They also face sampling and sample handling issues that have a great impact on the results. Indeed, the entire analytical process comes into play and students must work hard to bring the project to a successful conclusion. The instructor is kept busy as a consultant, helping students comprehend their task without interfering in the process of struggle that these projects demand of students. Several modes of reporting (oral reports, written reports, poster sessions) have been utilized during the years a special project has been done, and the poster session seems to provide the most rewarding experience for the students. Students are provided with detailed instructions about the size and format of the poster and the sections to be included in it. They are also given a description of how the event will be conducted and a set of criteria that will be used to evaluate their project and the poster. Each lab section has a two-hour session with half the students presenting their poster in each hour. During the presentation time the nonpresenting students are assigned to visit at least three other posters to ask questions and record both questions and the answers for submission. The instructor visits each poster with a checklist for evaluation. Other chemistry faculty are invited to attend (six faculty attended in a recent semester) to give students a chance to show their work to some more sophisticated attendees. The posters are retained by the instructor for a few days for further review to complete the grading of the project and the poster. The poster sessions are very positive and interesting sessions and the diversity of projects is impressive. When there are similar projects, the results and conclusions can be compared. The students take pride in displaying their work and most create fairly attractive posters and dress up for the presentation. The visits by outside faculty make the event more stimulating. All in all this is an excellent way for students to present their projects in a professional manner that is not too pressurepacked and to participate in a positive event at the end of 872

their laboratory work. Observations and Student Evaluations The process of helping students develop analytical skills is constantly evolving and the steps in this process have changed and will continue to change frequently. The process described provides an appropriate mix of support for the students and development of their independence. Decisions by the instructors about what to change and what to keep the same have been made by observing the results of the experiments and projects and by surveying student opinions about their experiences. Observations about the process and student development follow. Students learn to carry out appropriate data analysis and reporting in quantitative analysis. The student-defined lab reports and the special project posters demonstrate that. Most of the special projects in a recent semester showed that very competent decisions were made regarding what sort of data analysis to do, and the statistical analyses and conclusions were appropriate. The students learn to take responsibility and they gain confidence in their abilities as a result of the laboratory experience. Almost none of the students had previously done an analysis that meant anything to them and less than half had even heard of a poster session before the semester started. Yet the poster sessions were filled with interesting and welldone analytical projects and were well presented. Comments by faculty members who visited the poster session have been very positive with regard to the overall quality of the work and the perceived value of the event to students. Students learn to appreciate the level of commitment necessary to get analytical results that allow decisive statements to be made. During discussions at the poster sessions many of the students were aware of what they could and could not say about their results. There were also a significant number who needed to do more with their data or had some calculation errors that invalidated the reported results. During discussions these students recognized that they needed to do more work after the experiment to dig out the information that the analysis had to offer. Much progress has been made but there is more to be done. Two student surveys were done in a recent semester that shed some light on the students’ perceptions of their experiences. The first was done after the vitamin C (Exp. 6) write-up had been submitted and before the ISE (Exp. 7) write-up was submitted. It consisted of 10 Likert-scaled questions on lecture and 10 on lab (see Table 2). The second survey was a more general course evaluation that was administered on the last day of the semester. In both surveys students were given the opportunity to write comments on the back of the survey form. Based on the midsemester survey, students think the lab manual is usable (items 1 and 6) and most think the lab writeups help them understand quantitative analysis (item 2). However, fewer understand how the write-ups have been graded (item 7) and about a quarter don’t understand the write-up instructions (item 4). There are different ways to interpret these last two survey results. It could be that students are not given the information necessary to comprehend the grading. However, as each graded write-up is returned the students are given time to look it over, then each part of the grading scheme is explained and students are invited to ask questions

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in the lecture portion of the course, so the students must feel that they are working hard and not getting sufficiently high grades. However, most students said that their experience in lab was positive (iterm 10) and most said that the course is organized to help them learn the material. The interpretation is that that students are being challenged but understand that there is support and that the experiences are designed to help them learn. The end-of-semester evaluation has only one item that bears on this discussion. Thirty-seven of 38 students surveyed responded that the instructor stimulates independent thinking. This is interpreted to mean that they feel challenged to take responsibility for their learning and decision making in this course. Conclusions

either then or later. I believe that the students can understand the grading if they choose to. One possible improvement to the feedback would be to attach an itemized grading sheet to each graded write-up describing the criteria and points scored. The students who indicated that they did not understand the write-up instructions were probably struggling with the built-in ambiguity in those instructions. It is to be expected that some students are uncomfortable doing the write-ups because they haven’t been told specifically what to do and how to do it. Their discomfort is a necessary part of the development process and is to be expected. In written comments five students mentioned that the write-ups interfere with their learning, primarily owing to the fact that they don’t know “what the instructor wants”. Again the ambiguity of being forced to choose what to do and how to do it makes some students uncomfortable. The graded write-up for the first student-designed write-up, Experiment 6, is returned to the students before the second, Experiment 7, is due, which provides feedback on the objectives and expectations. The instructor is not insensitive to the student concerns, but sees the overall situation as one that aids in the development of analytical and reporting skills. In addition, many students think the reports are too long (item 8). The interpretation here is that students are coming to a realization of how much work is needed to analyze and draw conclusions from a set of data. Compared with their previous lab experiences the reports are quite long, particularly for those students who have not had organic chemistry. However, the length of the report is dictated by the tasks that are necessary to do a complete data reduction and statistical analysis so that appropriate conclusions can be drawn. Recently more effort has been made to educate students regarding the level of pre- and post-experiment work that is required to analyze and communicate results. These efforts have taken the form of comments in lecture and lab as well as devoting time to discussing student’s write-ups when they are handed back. Many students indicate that the laboratory grades don’t reflect their learning (item 3). The percentage was the same

Development of analytical and reporting skills can be encouraged in Quantitative Analysis by providing students instruction in the basics of analysis and data handling and then requiring the students to take responsibility for applying those basics to data they collect in laboratory. A variety of mechanisms can be used to help students recognize that they have the freedom and responsibility to choose to learn how to analyze and report experimental results. Although the teaching modes described in this article have required strong development efforts, they have not created a significant increase in workload. The time period during the special projects is intense, with a great deal of individual consultation. However the gradual increase in student responsibility during the semester results in the development of skills required to successfully work independently. Any extra effort required is gratifyingly paid off in the high quality of work and presentation seen in the special projects at the end of the semester. Acknowledgments Support for development of the cooperative group structure was provided by the National Science Foundation (DUE 91-50358). I thank Donald Campbell for help in the development of the course and this article. Literature Cited 1. Official Methods of Analysis of the Association of Official Analytical Chemists, 15th ed.; AOAC: Arlington, VA, 1990. 2. Harris, D. C. Quantitative Chemical Analysis, 4th ed.; Freeman: New York, 1995. 3. Pickering, M. J. Chem. Educ. 1987, 64, 521. 4. Mullin, J.; Eierman, R. J. J. Chem. Educ. 1990, 67, 878. 5. Wright, J. J. Chem. Educ. 1996, 73, 827. 6. A Handbook for Student Management Teams; Teaching Excellence Center, UW-Platteville: Platteville, WI, 1992. 7. Walters, J. P. Anal. Chem. 1991, 63, 977A, 1077A, 1179A. 8. Slavin, R. E. Psychol. Bull. 1983, 94, 429. 9. Zoller, U. J. Chem. Educ. 1987, 64, 510. 10. Campbell, D. L. J. Chem. Educ. 1991, 68, 784.

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