How to develop an informative comparison
Developing an investigation involves deciding what to compare and for what reason. This includes identifying and controlling variables, considering whether a comparison will provide information, and considering scale (e.g. how much to vary a factor to decide if it makes a difference). Engaging with how to develop an informative comparison helps children consider how their investigation procedures will help them answer their questions, consider multiple factors that might matter, and develop their understanding of scale and quantity.
A closer look at uncertainty in the classroom
Second graders are exploring materials they can use to test which of their seeds are good at traveling by sticking to animals. The teacher brings in several fabrics with differing prints and textures and asks them to think about which to use in their investigation. Then, she asks if tape will be useful. Children develop the idea of a test that provides information as compared to a test that makes something happen as they respond to the question, “Should we use tape to see if seeds stick?”
Should we use tape to see if seeds stick?
Lauren: I have something else I want to propose. Do you think that I should use tape to test if my seeds stick?
Students: Yes! (A few say “no”)
Yonas: Yeah, tape would definitely work.
Lauren: Sienna, I heard you say no. Why?
Sienna: Because we’re trying to see if it sticks, not MAKE it stick. We don’t want to have science that’s not actually true. We want to learn if it will actually stick, we don’t want it to be like magnets that stick together on their own.
5 students raise their hands; Felisa is enthusiastically waving her hand & using the “I agree” symbol
Lauren: Felisa, it looks like you agree with Sienna. What would you add on to her idea?
Felisa: It’s not going to give you that much information. It’s not really gonna give you that much information about the seed.
Lauren: So you’re agreeing and adding to Sienna’s idea. It’s not going to teach us anything more about the seed.
Yonas: If there were no spikes on the seed it would still stick. It’s like glue.
Lauren: You think the tape is like the glue, and everything will stick to it. So do you think it’s something we should use?
Yonas: It just tells you that the tape can hold it on.
Instructional moves to support this form of uncertainty
Ask children to play their investigations into the future: “If we do this and x happens, what will we know? How about if y happens?”
Use outrageous procedures: show children a confounded or uninformative comparison and use it make a claim (My seed is a good sticker! Cold temperatures support decomposition!) then ask children if they agree or to provide a critique.
Allow students the experience of conducting an uninformative investigation and experiencing pushback from the world or disagreement about claims, then ask them to propose revisions after they have made sense of ambiguity in their evidence.
Name and record quantities and scale regularly in the classroom and keep these visible - for example a thermometer that records the different temperatures used in the investigation. These help students reflect on the scales of variables they are using in their investigations (e.g., if they have varied temperature enough to make a claim about whether heat can melt a rock).
Where else does this form of uncertainty come up?
Explore Related Cases
Other Ways to Learn More
Take a look at the support provided for students to plan informative comparisons in Decomposition Lesson 5 and the Decomposition Student Notebook.
Explore the Planning Investigations Conversation Tool.
See the example in How to Generalize for how a teacher helps children reflect on whether their investigation has generated information about whether heat can change the state of rock.
