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TA Guide to Guiding Labs

Page history last edited by Kim Moore 9 years, 2 months ago

TA Guide to Guiding Labs (with elements drawn from E.F. Redish's: http://umdperg.pbworks.com/w/page/10511170/121-122%20Reformed%20Labs)

 

(For more information on the NEXUS/Physics labs, you can see our paper: K. Moore, J. Giannini & W. Losert "Toward better physics labs for future biologists," Am. J. Phys. 82 (5), May 2014 (http://dx.doi.org/10.1119/1.4870388), or the early draft on arXiv: http://arxiv.org/abs/1308.3882 .)

 

What happens in NEXUS/Physics Labs?

 

            We have developed a set of laboratories and hands on activities to accompany NEXUS/Physics.  We have designed the laboratories to be taken accompanying a reformed course in the student's second year, with calculus, biology, and chemistry as prerequisites.  This permits the laboratories to include significant content on physics relevant to cellular scales, from chemical interactions to random motion and charge screening in fluids.  We also introduce the students to research-grade equipment and modern physics analysis tools in contexts relevant to biology, while maintaining the pedagogically valuable open-ended laboratory structure of Scientific Community Labs (SCL). 

 

            In these labs, students are presented with a challenge/question.  Students then work in groups of four to develop their own experimental protocol (design), gather and analyze their data, and present their work to their classmates, providing insightful questions and critiques, before producing a lab report summarizing their work on the lab (one report per group).  Most of these labs are two weeks (four hours total): week 1 for designing the experiment and gathering the data, and week 2 for analyzing, presenting, and finalizing a report.  The lab is set up to mimic the actual process of scientific experimentation, so:

    • They may have to do the experiment before they have "learned the answer";
    • They have to work as a cohesive group;
    • They have to present their work to peers; and
    • They have to learn to give and take constructive criticism. 

 

            We aim to retain the epistemic (learning about knowledge) gains sought by other reformed lab curricula while seeking changes that particularly benefit our target student demographic (life sciences majors):

·         a focus on physics relevant to microscopic and living systems;

·         the use of 21st century tools and software;

·         the ability to engage with data-rich environments; and

·       preparation for future contributions to biomedical research.

 

  

            In addition to these benefits and the lab skills called for in Competency E2 of the HHMI-NEXUS project (i.e., Demonstrate understanding of the process of scientific inquiry, and explain how scientific knowledge is discovered and validated),3 the development of the lab curriculum focuses on five main threads: modeling; experimental design/protocol development; error analysis; technical lab skills; and interdisciplinary thinking.

 

            A. Modeling

            Crucial to a scientific mode of thinking and to the development of deep and meaningful understanding of science content is the ability to engage in modeling.  Models come in many forms (conceptual, physical, mathematical, diagrammatic, graphical, et al.), but all share some basic elements.  Students must learn to choose which aspects of a system to model, to choose appropriate representations of these aspects, to make predictions based on their model, and to determine the limitations of their models (where and why a model breaks down).

 

            B. Experimental Design / Protocol Development

            The ability to design and carry out an experiment is a hallmark of scientific thinking, whether or not one becomes an experimental scientist.  In the biomedical sciences, experimental design is often referred to as protocol development and is a highly prized skill both for future biologists and for medical researchers.  Yet the skills required to design an experiment/protocol are often ignored in lab curricula across the sciences, leaving undergraduate science majors with no specific training in these skills.  By presenting students with a question to answer and minimal guidance (mostly in the form of how to use the high-technology equipment), these open-ended labs encourage students to build these crucial skills.

 

            C. Error Analysis

            As Kung, one of the developers of the SCL reformed labs, notes: "Many laboratory courses teach students the mathematics of uncertainty analysis such as the arithmetic mean, standard deviation, and percent error, but students are rarely able to use these constructs to make a strong argument from their data.  Even worse, using such tools without understanding may be detrimental to future development of understanding."  Thus we have made an effort to raise issues of error analysis in contexts that clearly demonstrate how this skill can help choose amongst competing models of a phenomenon and also translate the challenges of measurement into meaningful interpretation of results.

 

            D. Technical Lab Skills

            Alongside the epistemological framework we present to our students, it is important that they gain practical, technical skills that they will be able to apply in professional contexts.  To this end, half of our labs employ an inverted microscope with CCD camera for collecting high-resolution, real-time videos of microscale phenomena.  Analysis of such data-rich videos requires an image analysis software, such as NIH's ImageJ (used widely in biomedical research labs), and sophisticated facility with spreadsheet programs.  Students are given explicit, extensive support on the acquisition and application of these technical skills, leaving them more time and energy to devote to the open-ended experimental design and data interpretation (for which very few protocols are provided).  The other significant high-tech equipment is a USB Infrared to UV spectrometer that collects and displays data in real-time, which is used in labs 10 and 11 in the second semester.

 

            E. Interdisciplinary Thinking

            As with other aspects of the NEXUS/Physics project, interdisciplinary thinking is an important aspect of these labs.  We aim to foster this connection by carefully choosing laboratory topics and measurement contexts.  We also reinforce this thinking by connecting labs where the focus is on physical systems and measurements with labs where physics is measured directly on living.  With this scaffolding, we are in a position to ask students to consider what biology can be learned from a physical measurement.  They are also asked to seek the biological authenticity in each scenario and to recall, reconsider, and revise their understanding of science content learned in previous courses.  It is this thread, together with the specific high-tech tools and modern analysis methods, that most distinguish this new curriculum from the traditional and other reformed lab curricula.

 

What are the goals of NEXUS/Physics Labs?

 

These labs are very different from the traditional 'cookbook' labs.

            A laboratory can fulfill a wide variety of purposes.  Traditional labs often teach students to follow protocols or are intended to demonstrate that the theory taught in lecture "actually works."  Our labs in NEXUS/Physics have a different set of goals.

 

The goals of these labs are to help the students:

·         Learn to design their own experiment,

·         Learn how to improve on their experimental protocol (given what they learn as they collect and analyze data and critique their experiment with the larger class),

·         Learn to interpret experimental data (including: understanding how the design of an experiment affects the 'knowability' of the result; error analysis concepts),

·         Understand concepts better (including a strong emphasis on modeling skills),

·         Learn to work with other people,

·         Learn to communicate ideas in different ways, and

·         Prepare for their future professional career (including both technical lab skills and interdisciplinary thinking).

 

What is the role of the TA in these labs?

 

The TA is critical in "setting the frame" and helping the students understand what it is they are trying to accomplish.  You have a number of tasks.

  1. Focus them on the activity, not on the answer.

Since the students are very concerned about their grades they tend to focus on "how to get the answer the grader wants."  We want them to focus not on the answer but on the process of doing science. 

  1. Grade them on the quality of their process, not on the answer they get.

You should make it clear to the students that their grade on their report will be based NOT on whether they get the "right answer" but on whether they have done a well-thought out and careful experiment.

  1. Keep their attention on how the experiment is getting the answer to the question.

Your goal is to have each student engaged with creating and doing their experiment with their group.  Students (and faculty!) can easily get trapped in the technicality of an experiment they have designed without sufficient thought.  If you see them on a dramatically wrong track, the following questions can help:

    • What are you doing?
    • Why are you doing it?
    • If you succeed, how will you get the answer to the question you are investigating?
    • What else could you try?

    4.   Keep an eye on the time so that there is enough time (45-60 minutes) for presentations, discussion, and finalizing the lab report.

The students can easily work on their experiment for the full four-hour block.  Make an effort to keep them on track and moving along so that there is time to prepare and deliver the presentation, have a discussion, and finalize their report.

  1. Help them participate in a spirited, interactive, and productive discussion.

Many of the students in the class don't know how to have a scientific discussion -- how to focus on the argument and not make criticisms personal.  Many are reluctant to say anything for fear of saying something wrong.  It is important for you to create an environment in which they are comfortable discussing how one might improve each group's experiment.  This is easier said than done.  If you provide too much guidance, they will rely too much on you.  If you provide not enough, they might hang back and not contribute enough.  Finding the right balance is tricky and can depend on the students you have in your section.  Your goal is to have them excited and engaged in the discussion and for you to disappear into the woodwork as an observer, not as the leader.

 

Your grading pattern is very important.

  1. Set a high standard from the first and clearly explain what you expect and where they fall short.

Our experience shows that students have mostly not had labs like this before and don't know what to do.  If you don't demand real science from them they will interpret the instructions as "just mess around."

  1. Your grading should give the students feedback on what you want them to do.

This is particularly important in the first and second labs where the students are figuring out what is expected.

  1. Don't "ramp up" your grading right away.  If they improve let them see it in improved grades.

Some TAs have started with critical comments and then, as students met those criticisms, brought in new criticisms to create more improvement.  This can be very frustrating for students and is one reason why your initial lab grading should be severe -- to allow room for improvement.

  1. Grades should be given for good thinking and presentation, not answers.   

These labs are supposed to have students exploring topics experimentally where they do not yet know the answers.  For this to work, it is necessary that you reward a well planned and executed attempt even if it turns out not to work for some reason that they could not have foreseen.

  1. It is crucial for this lab that your grades show a significant distribution (standard deviation). 

If you are giving nearly perfect grades to everyone it means your standards aren't high enough!  Expect more!  Worse, part of having a lab of this sophistication and complexity is to allow students with a variety of skills to succeed in the class.  Some students are poor test-takers but excellent experimentalists.  If you don't allow them to stand out in lab, you rob them of the opportunity to do well in the class despite their trouble with exams.  

  1. Let them know what the components of your grading are for.     

 Here's a good pattern.

          -- Design and thoughtfulness.  (7.5 pts -- for group report)

               Did they do a careful and thoughtful job in creating their experiment and was this thought reflected in the journal?

          -- Clarity and completeness. (7.5 pts -- for group report)

               Did they explain the experiment so that someone else could reproduce it?

          -- Persuasiveness.  (7.5 pts -- for group report)

               What conclusions did they draw from their data and were they able to back up these conclusions with their data in a convincing way?

          -- Evaluation and Prospection. (7.5 pts -- for group report)

               After the group discussions it is useful to give the group 5-10 minutes to write a one-page "How I would do this experiment differently if I had to do it again."  This will encourage them to pay attention and take notes during the discussion and will help them learn to evaluate their work.  They should also critique their choices in experimental design and data collection and analysis and showcase their interdisciplinary thinking.

          -- Participation. (3 pts per week  -- for individual)

               This is not from the report (and NOT solely for participation in the design and carrying out of the lab) but from participation in the end-of-lab presentations and discussion.  These points are for actively participating in the presentation and delivery and for asking  useful questions or making comments that were valuable to the other teams’ write-ups of their evaluations.

 

EXAMPLE RUBRIC: Hints to TAs for grading lab reports

 

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