NSTA discussion thread about hypothesis

On Sep 6, 2008, xx wrote:

A few years ago, Bill Harwood and a couple of graduate students interviewed me and a whole bunch of others, to find out what we do. This was actually the first time I heard the word "inquiry" applied to science or to teaching. Eventually, they sorted the various things we all do into categories they could name. They talked about it in meetings, and eventually Bill refined the model, as described in "A New Model for Inquiry" W. S. Harwood, Journal of College Science Teaching , Jul 04. In this paper, Bill walks through the investigation described in "Inquiry and the National Science Education Standards." We can walk through any investigation with this model, including those in various movies and videos we show in class. The bottom line is that everyone jumps around a lot as they work through things. This is really useful for students, I think. Even in those fields that follow the Official Scientific Method still jump around a lot in practice.

The format of publishing the paper, however, creates some interesting constraints. Ecology requires, as if by law, that one state one's hypothesis and the predictions made by the hypothesis in the Introduction. The Methods section is everything about what one did. Results can be really minimal, such as (and I quote a real results section here), "The result of experiment 1 is shown in figure 1. The result of experiment 2 is shown in figure 2." The Discussion is dedicated to assessing how well the results match the predictions.

This is the Scientific Method. Some of my ecology colleagues do, in fact, say that their hypotheses really are "educated guesses." They have collected as much data as they can, and they are doing their dangedest to interpret it correctly. But since they can't look up the answer in the back of the book, they can't know their interpretation is Right. To these people, it seems that "educated guess" is a good description.

By contrast, the Journal of Biological Chemistry shuns the Scientific Method format. The Methods section is only the protocols for the experiments, and absolutely nothing about the logic and design of the experiments. It is even relegated to a small-font appendix at the end of the paper, which no one is expected to read unless they want to know the pH of the solution, or some such technical bit. All of the logic and experimental design is presented in the Results section--because it is expected that the paper will describe a series of experiments in which one follows the other. If you've got 10 experiments in a row, there's no way you can describe in the Introduction the hypothesis you're testing in the tenth experiment. All of the data for building that hypothesis come from experiments 1-9.

Comparing these things to the inquiry model in Bill's paper, it seems that the "scientific method" still exists in biochemistry, but as a kind of subroutine that everyone follows for each experiment. If I am running a bunch of restriction digests on a gel, each lane of the gel is an independent instance of following the scientific method. Each lane tests a different sample. For each sample, there's a hypothesis about what the DNA sample is, and a prediction based on that hypothesis about the sizes of the DNA fragments after the restriction digest. I look at the gel afterwards, and compare what I see with what I expected, and then throw away the samples that don't match. In this case, the hypothesis is "the plasmid has this particular structure and sequence, which has EcoRI sites in these particular locations." The prediction based on this hypothesis is that the EcoRI fragments will be exactly the sizes that result from that particular structure and sequence. Neither the hypothesis nor the prediction have anything to do with guessing, educated or not. For each sample, I'm asking "does this plasmid have this structure and sequence?"

But the Big Experiment may not have a clear prediction. Marshall Nierenberg simply could not predict what amino acid would be polymerized in a cell-extract given synthetic RNA composed entirely of U. There were 20 equally likely choices. We can predict that one of the amino acids will be built into protein, but if we already know that RNA codes for protein, then this isn't much of a prediction. Here, it makes sense only to ask a question: "what does poly-U code for?" It turns out to be poly-phenylalanine.

I suspect that the "random guessing" that bothers me so much is more common in elementary science. Look at the Great Growing Beans lesson plan on the Indiana DOE website. It asks the kids to take two beans, and with no prior discussion of seed biology, predict which one will grow faster. "I think the white one will grow faster than the brown one." The exercise is to water them, and measure them every day, and then make a graph. Then, they decide whether they guessed right. "Nope. The brown one grew faster." [Actually, in the case of the student I know, the answer was "Nope. They both died."] So, for this lab, I wonder what science we're trying to teach.

But I digress.

Bill Harwood's paper does a good job of illustrating that science doesn't follow a clear, linear path. One can follow the linear Scientific Method if one wants--and my ecology friends tend to come much closer to doing so than I do--but it's not "required" and it's not absolute. The particular path we follow when doing science depends heavily on the nature of the investigation (eg. ecology vs biochemistry), the things we discover along the way, and the things that other people discover that influence our thinking.

On Sep 6, 2008, yy wrote:

Hello everyone,

I have noticed a lot of dynamic changes in how we approach teaching the scientific method and the parts and pieces involved. I love to compare available texts and how they approach particular topics. Somewhere I came across a statement that there is no specific scientific method. Each taxonomy of science has their own and each scientist is unique in how they approach a problem or observation. In teaching we have become hung up on the "science fair approach." I am convinced that there is a difference between hypothesis and prediction and that as a teacher it is my responsibility to teach my students the difference. I have also become a fanatic about "hypothesis is an educated guess." I sometimes think my students bring that out to see my reaction. I sent my youngest running when I confronted her teacher to not teach that disgusting tripe. I was more diplomatic than that but I was also able to cite The Lingo of Learning by Alan Colburn from NSTA Press. The teacher was correct in demanding some proof that she was wrong and I was right. I have also come to see this is an uphill battle because many future teachers are still taught this in college and publishers are still publishing the "correct" order of the scientific method. The scientific method is a starting place for research especially with students who have no experience. As a scientist matures both in education and experience they are weaned from the traditional method and understand that the important parts of research is not to plagarize, to support your data and it must be repeatable by other scientists. As a result of my personal educational review I teach that an hypothesis is "a statement that can be tested." A (scientific) theory is "a generally accepted scientific principle" and is subject to change based on new technology and information and a prediction is "an educated guess" or an "I think..." statement. What I really want them to understand is that there is no set in stone scientific method.

September 6, 2008
Subject: Re: hypothesis statement

Well, I guess that we're now nuancing "prediction," too. Not a problem, but something worth discussing.

Upon reflection, I have asked my students to predict the outcome of some particular procedure (demonstrated by me, done by students in a lab, or just as a thought exercise). I do this for different reasons. Sometimes it's to see if they apply previous learning (previous class work or reading assignment), and sometimes to expose misconceptions or false assumptions (often a part of using discrepant events to engage or intrigue students). I agree with José that a formal prediction for the outcome of an experimental test (or proposed search for evidence) must be based on previous observations (experience). But is this so different from the previous experiences we all bring to any anticipated event? There may be great variation in sophistication and detail of those experiences, but we all have them.

I also agree that the process of predicting the outcome of a particular operation can influence our perceptions of what we experience. As José points out, this can get in the way of optimal objectivity in some types of studies, but in other kinds it can also enhance and focus observations so we will see things that might otherwise go unnoticed because they are so subtle.

So, just as different variations on the processes of science are applied differently to different issues in different fields of science, expectations will exist, but their form and level of detail will vary, and may be helpful, or a hindrance, possibly unduly influencing the results, their observations, and/or their interpretations. Most importantly, good science must recognize these factors, and proceed accordingly.

Like Consuelo, I often have students do a lab in order to experience a phenomenon without any focused preconceptions, to be followed by guided discussion and often reading about it to further relate the meaning of that experience into formal terminology (part of the 5E's). Nevertheless, from time to time, I feel it's important to increase mental engagement ('minds-on") in what is happening ("hands-on"), often asking students to RECORD (commit themselves on paper) what they expect to happen (in a demo or lab), and even provide a substantive reason for that prediction, not just "because" or that "it's logical". Ideally, this prediction will be based on a valid understanding of the mechanism at work in a particular phenomenon (their "hypothesis"). When a misconception leads to a prediction that is inconsistent with the results of a procedure, this personal disconnect can be a powerful influence on repairing that misconception. In fact, this may be the only way we can get kids to change their misconceptions.

On Sat, Sep 6, 2008 xx wrote:

That's a good idea, Laurie. It really would help to know how students come up with their expectations. Asking them to articulate a "because" statement would do this.

I wonder, though, whether it's possible or even sensible, in terms of hypothesis testing, to ask them to make a prediction about something they know little about. Consuelo, you mention that students don't have advance reading assignments, so they discover the new information as they do the investigation in class. That's good, in the sense that doing a lab before reading (and memorizing facts about it) seems to make the labs more interesting. It also makes the information stick better when they do read it, because they have some experience to relate it to. But, do they have any basis at all for a prediction?

In hypothesis testing (aka "the" scientific method), the prediction is not what you think will happen; it's what must happen if your current understanding is correct--that is, if your hypothesis is true. If you don't have an hypothesis, you can't make a prediction. If you don't have prior data, you have nothing to explain, and thus no hypothesis.

I think we've gone astray pretty seriously in our presentation of scientific method. It's very common in lesson plans to ask students to predict what's going to happen when the teacher (or they) do something new. "I have a can of regular Coke and a can of diet Coke. I'm going to put them both into water. Which one do you think is going to sink?" If we ask them to predict the result of an experiment when they know nothing about it, all they can do is guess. Predicting outcomes by guessing is very much the opposite of doing science.

That's part of the reason I prefer asking questions. "I have these two cans of Coke. Let's put them into water (or better, I opened my cooler the next morning after the ice had melted, and this is what I discovered). Yikes! Look at that. The diet Coke floats, but the regular Coke sinks. What the heck? What could account for this?" Now the kids have observations. They can gather data (read the list of ingredients and the so-called nutrition "facts"), and build an explanation.

The only way to use the Coke can bit to predict an outcome "scientifically" is to start by studying density, sugar solutions, cans with an air pocket in them, etc. Then the students can base their prediction on their knowledge of density and the contents of the cans. This approach would be much less exciting, though. It's more fun to discover something weird, and then figure it out. But if it's weird and unexpected, and they haven't seen it before, do they have any basis for a prediction?

On Sep 6, 2008,   wrote:

[NSTA Biology]

Consuela -

I teach several levels of high school science and I think that the 'because' part of the prediction can arise from either relevant readings or prior investigations OR, even more importantly in my view, it can arise from a student's currently held belief. Figuring out why students make assumptions is helpful when trying to teach correct science...sometimes something they think is 'true' is not, or sometimes they think phenomenon are related when they are not. For my lowest students, I only ask that the prediction not be totally random: they must give me a reason they think the outcome will be such and such. Older students, yes, they have to tie in something from our current topic (or prior, even better!) that leads them to make their prediction. Either way, there is lots to 'discuss' in the final section when they critique their method and either validate or disprove their own prediction.

[NSTA Biology]

I have been part of a program called RIP (Research Investigation Process)

designed by Robert E. Landsman (ANOVA Science Education Corporation).  This

is a science teacher training program for a DOE District in Honolulu

(KaimukiDistrict).  Dr. Landsman teaches that a hypothesis statement must be

of the form:  If so... then so....because....

I have questioned the "because..." part of the statement.  Our students in

Modeling do not have advance reading assignments, i.e. no reading about a

concept until they have done the investigation and formulated their

discovery (new knowledge to them).  The "because.." part means that the

student had done "research" on the subject and most likely going to test the

information s/he had read about.  I do not see this as  different from

"proving a scientific fact/law".

Dr. Landsman's point is that scientists base their investigative research

on previous knowledge.

What do you folks think about this?