• If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.

  • Dokkio Sidebar (from the makers of PBworks) is a Chrome extension that eliminates the need for endless browser tabs. You can search all your online stuff without any extra effort. And Sidebar was #1 on Product Hunt! Check out what people are saying by clicking here.


121-122 Reformed Labs

Page history last edited by Joe Redish 12 years, 7 months ago

These labs are very different from the traditional.

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 121-122 have a different goal.

  • The goal of the SCL is to help the student learn
    • How to design an experiment to answer a question;
    • How the design can affect the quality of an experimental result;
    • That each measurement tells a range of possible answers and how to determine that range;
    • How to refine their experiment in order to improve it.


  • 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 present their work to peers; and
    • They have to learn to give and take constructive criticism.


Since the lab is set up to create a model of a "scientific community" for the students, we refer to them as Scientific Community Labs (SCL).


The SCL is not structured as following a protocol.

The SCL lab is structured to help the students get the experience of learning something through a scientific experiment.  Here's the structure:

  1. Students work in groups of 4 and construct a single lab report among them.
  2. The have two 2-hour periods to complete a single lab.
  3. In the first period, they design their experiment, construct the apparatus, and take their data.
  4. In the second period, they analyze it and create a presentation for the entire class of their results.
  5. In the last hour of the second period there should be a presentation by each group and a discussion.
  6. The last 10 minutes should be reserved to have the students finalize their report. 


Writing the report

Each group should assign one member to write each of the four parts of the report -- and they should rotate those roles through the term. The roles are:

  • Describing the design
  • Presenting the data
  • Analyzing the data
  • Evaluation the experiment after the whole-class discussion.


What's the TA's job in an SCL?

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. 

  2. 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.  In your grading you should encourage "good tries" that did not work but that they could not have been expected to know would not work. 
  3. 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?
  4. Keep an eye on the time so that there is enough time (45-60 minutes) for presentations and discussion.

    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 and have a discussion.

  5. 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 what students you have.  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."

  2. 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.

  3. 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.

  4. 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.

  5. It is crucial for this lab that you 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.  

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

     Here's a good pattern.

          -- Design and thoughtfulness.  (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. (5 pts -- for group report)

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

          -- Persuasiveness.  (5 pts -- for group report)

               What conclusions did they draw from their data, and were thet able to back up

               these conclusions with their data in a convincing way?

          -- Evaluation and Prospection. (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.


          -- Participation. (5 pts  -- for individual)

               This is not from the report (and NOT for participation in the design and

               carrying out of the lab) but from the end-of-lab discussion ONLY.  

               These points are for actively participating in the presentation and delivery (max 2)

               and for asking  useful questions or making comments that were valuable

               to the other teams’ writeups of their evaluations (max 3).


121-122 TA Guidlines (Redish) 


Comments (0)

You don't have permission to comment on this page.