While students do forensics, I dissect the class

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Sandra Porter

The blood typing lab, part I. What went wrong? and why?
Blood typing part II. Can this laboratory be saved?

Those wacky non-major Zoo students are at it again! And this time they drew blood!

Mike's undergraduate students learned about blood typing, a common tool of detectives and real crime TV. They did the classic blood typing lab, and by golly, they refused to parrot the correct answer on the test! The nerve! After all, he pretty much told them the answer and even used the exact same wording that was used on the test question. Why didn't the students just memorize it and regurgitate?

Can a scientific approach to teaching can help us out?

How do we do that?

First, a quick summary of the class activity:
The students pricked their fingers and determined their own blood types. Mike told them that a mother with type AB blood could not have a child with type O blood. In one section of the class 25% of the students got the question wrong, in the other section 20% got it wrong.

Q: What were the experimental treatments?

A: 1. The students did an activity with blood typing.
2. Their instructor shared verbal information.

Q: What was the expected outcome?

A: I'm not certain, but I think Mike expected all the students to get the right answer.

Q: What was the actual outcome?

A: Between 75 and 80% of the students got the correct answer on the test.

What do we do next?

What do you when an experiment doesn't work the way you expected?

A: Hmmm. I try to figure out which step went wrong and then I try to find out why it went wrong.

How do we do that? What can we try?

We can start by reevaluating our assumptions and expectations. Were they correct?

1. Assumption one: Too many students (20-25% in the two sections) got the question wrong.

And 75-80% of the students got the question right. Is that abnormally low? Mike could look at historical data and query other people who've taught the class. If it were me, I would be satisfied with those numbers, especially with non-science majors.

You're not very much help. Mike wants to do better! Is there anything else can we learn?

It would be helpful, for future classes if nothing else, to know why students are getting the wrong answer. Mike could survey, or interview, the students, who gave incorrect answers and try to find out what happened.

I think he would find that students fall into the following groups:

1. Those who weren't paying attention or didn't do the assignment.
2. Those who didn't understand the question.
3. Those who got the question wrong but can't explain why (probably because they haven't learned how to speak "biology."
4. Those who got it wrong and can articulate the reason.

The last two groups could provide some help in identifying specific things that got them off track, but it does take time to develop the interviewing skills that help you get at the information.

Let's tackle the second assumption.

What second assumption?

See if you can guess it from my selectively chosen quotes:

I did a lecture prior to the experiment, and went over blood group inheritance. I went over blood group inheritance again with students on a one-on-one basis during the experiment, while looking at their results.


At the end of that, I reminded them that an AB parent couldn't have an O child...

Okay, here's the answer:

Assumption two: Telling students the correct answer will cause them to give the correct answer on a test.

There are other methods of teaching that are known to be more effective than "telling the students the answer." I'll come back to those later on.

Mike even did a small pilot test, and used a different teaching method with 25% of his class:

.. had about a quarter of the students tell me what their blood type was, and what bloodtypes their parents could not have.

Making students explain concepts in their own words is a well-established and validated method for reinforcing learning, plus it gives the instructor a nice assessment tool.

This is another place where we could use a scientific approach. If Mike had jotted down the names of those students, we could ask if those students did better, worse, or the same as the students who weren't asked to state their conclusions out loud and explain their answers.

There is a large body of research that shows that students learn and understand concepts better through methods of active and/or inquiry-based teaching than they do from being told the answer. These methods involve having students interact with the material through activities like:

* having students state the problem and answers in their own words,
* having students complete problem sets and homework,
* using lab activities that guide students towards discovering the answer themselves.

How could we add some active-learning methods to the blood typing activity ?

If you have ideas, jot them in the comments. Or check back later and I'll show you mine.