The skill of fair testing was also an important prerequisite for students to be able to conduct their bean plant investigation therefore Stella carefully guided
Skills necessary for conducting their investigation. Following revision of the skill of observation in lesson four, Stella planned a second “We do it” phase in which she focused on scaffolding students’ understanding of fair testing. Again, she used questioning as a strategy in the “We do it” phase to promote rich teacher- to-student dialogue to engage students in reflecting on their own bean seed investigation, however, this was combined with detailed explanations about potential problems that could impact on whether a test is fair or not (Transaction 7). Stella uses a PowerPoint slide: Investigation in Science: Cows Moo Softly and also makes reference to the fair test poster as a cue in the following excerpt.
Transaction 7: Stella revises the skill of fair testing in the “We do it” phase of lesson 4
01 Stella Why have I put this slide up? What is so important as we’re getting to that stage in the investigation where we’re starting to write our investigation? Why is this slide so important? (points to slide that says “Cows Moo Softly”)
02 Sally It says Cows, Moo, Softly and Cows means what are we going to change in our investigation and Moo means what do we measure in our investigation and Softly means what do we keep the same in our investigation.
03 Stella Excellent. What would you like to say Eliza? 04 Eliza Um, it’s like the rule for a fair test.
05 Stella It is. It’s exactly right. It’s our rules for our fair test and when William [student in Tasmania science team] came to me this morning and said my plant’s been knocked over again and you were talking about something not being right what were you thinking of Will?
06 William Ah, the measurements and two things had changed.
that we have to keep everything else the same. So we’ve had a bit of a problem with that particular group [Tasmania science team] because they’ve lost some soil and their plant’s not...if it was going to be the same then somebody shouldn’t have kicked all these plants over which of course we wouldn’t do. So when we’re investigating in science...and one of the reasons I wanted to bring this to your attention is you just can’t put your plant, your seeds in the cup and forget about them. Ok, you need to look after them. So if you’re giving the plant in the cup that we’re putting out on the patio, out on the porch, out there…if you’re giving it thirty millilitres of water each day what should you be doing with your other two cups?
08 Ellen Yes, giving it thirty millilitres of water each day.
09 Stella Ok, good. So the plants that are in my fridge have you been watering those? Ok you need to make sure you’re still watering those cups. The cups in the cupboard; Hands up if you’ve been watering the cups in the cupboard, (one hand went up) the same amount as the cups outside?
10 Lana Yes.
11 Stella Excellent. Ok, one of the problems that we found in previous years is if you water them the same amount and the cups that aren’t out getting nice and warm out in the sun and aren’t having that chance to evaporate then those bean seeds can rot. Once we had some of the seeds rotting in the tissue. So what you might like to do rather than saying you’re going to measure the same amount of water into the cup each day you could say that you’re going to test that the soil has the same moisture level in it. It’s the same wetness. You might like to think about that so when we get onto our experiment and …we’re looking at our cups today, I’ll come and talk to your group about that. Ok, but just keep in mind we only want to change one thing. Everything else has to stay the same. So change one thing, measuring
something. Are we going to be doing any measurements today for our investigation with three cups?
12 Students No.
13 Stella No we’re not. Ok, we’re only going to be measuring them at the end of the investigation. But we are going to do today is we want to check and make sure we’re doing a fair test because I think for a few people, for a few science teams, we’re not following up on that enough. So we’ll check with that today and of course this is the one that’s most important. Let’s make sure we keep
everything else the same. Where have we seen that writing? Does anyone recognise that writing?
14 Sally In a test.
15 Stella Yes we did it in a test the other day.
16 Polly Up here (Student points to poster on window).
17 Stella Yes that’s right. I’ve taken little screen shots. Ok, so if we go back there’s that gorgeous little cow. Ok, that’s the same as up on the poster. Ok, so any time you need to refer to this
information you need to go back to those posters.
In this excerpt Stella made reference to the PowerPoint slide of Cows, Moo, Softly and (Transaction 7, Utterance 01) and questioned students to draw out their understanding of fair testing. One student responded with a clear
definition for the process of fair testing as evidenced in Utterance 02. Next, Stella explicitly explained her thinking to clarify for students the process of fair testing and also demonstrated how to tackle the decisions necessary to
successfully complete a fair test as evidenced by her reference to the problems experienced by Will (Transaction 7, Utterance 06) and also explaining one of the problems that was found in previous years (Transaction 7, Utterance 11). Stella used the PowerPoint slides as well as the fair test poster on the
classroom window as cues during this excerpt (Transaction 7, Utterance 17). When teaching and revising the Science Inquiry Skills and during investigations,
cues of all the thinking about the Science Inquiry Skills that was represented on the posters.
4.3.6. Questioning students while they practise the skill of fair testing in