ACARA v9 CONTENT DESCRIPTION “plan and conduct repeatable investigations to answer questions, including, as appropriate, deciding the variables to be changed, measured and controlled in fair tests; describing potential risks; planning for the safe use of equipment and materials; and identifying required permissions to conduct investigations on Country/Place”
Builds on earlier fair-test planning. Now you plan an investigation that you can repeat: you decide which variable to change, which to measure, and which to keep controlled, you describe the risks, you set the equipment up safely, and you work out what permissions you need before investigating on Country or Place.
The sediment-and-slope investigation
You want to find out how the slope of the ground changes how far sediment travels in flowing water. This is what happens to soil washed down a hillside in the rain. You build a tray of soil, pour the same amount of water from the same height, and measure how far the sediment travels down the tray. The one thing you change is the slope: the steepness you tilt the tray. Everything else, the water, the soil and the pour height, you keep the same.
Changed, measured, controlled
A repeatable investigation names three kinds of variable. The variable you change is the slope. The variable you measure is how far the sediment travels. The variables you control are kept the same every run: the amount of water, the type of soil, and the height you pour from. When only the slope changes, any difference in distance must be due to the slope.
Plan the sediment test: change the slope, control the rest
You are testing how the slope changes how far sediment travels. Choose the one variable you change, and keep every other variable controlled.
One tray of soil, one jug of water poured from a set height, and three slopes to try: gentle, medium and steep. You want to find out how slope alone changes how far the sediment travels, so every other variable must be kept the same.
Variable being tested: The slope of the tray (how steeply it is tilted) (this one we change)
The amount of water you pour (use the same amount every run)
The type of soil in the tray (use the same soil every run)
The height you pour the water from (pour from the same height)
Not a fair test yet: more than one thing is changing, so you could not tell which change caused the result. Hold every other variable the same.
Repeating trials and naming the risks
One run can give an odd result. Repeating each slope three times and taking the middle value makes the investigation repeatable: if the distance comes out close each time, you can trust it. Planning safely also means describing the risks first. Spilled water makes the floor slippery, and a heavy tray of wet soil can be awkward to lift. You choose equipment and a setup that lets you repeat trials and keeps everyone safe.
Pick the setup that lets you repeat trials safely
You need a way to run the slope test three times at each slope without spills and without a heavy lift. Choose a setup, and see what each one gives and gives up.
How you set the tray up decides whether you can repeat the test cleanly and whether it is safe. Some setups make repeating easy and tidy; others save effort now but cause spills or an unsafe lift.
Choose a response to see what is gained and what is given up.
Permission to investigate on Country or Place
To collect soil from a creek bank in bushland, you may need to investigate on Country or Place. This land is cared for by custodians, including the Aboriginal and Torres Strait Islander Traditional Owners. The responsible planning step is to seek permission before you go, take only what you need, and respect the land and the people who care for it. Asking permission is part of planning the investigation, just like naming the risks and setting up the equipment safely.
Which actions make the investigation repeatable, safe and properly permissioned?
A good plan has actions that make the test repeatable, actions that keep you safe, and the step of seeking permission before investigating on Country or Place. Some things you might do have nothing to do with any of these. Sort each action by whether it really helps, or whether it is beside the point.
Sort the planning actions for the sediment investigation
The plan: pour water down a tray of soil at different slopes to see how far sediment travels, collecting soil from a creek bank in bushland. Decide which actions make the investigation repeatable, safe and properly permissioned, and which do not.
Claim: To investigate how slope changes how far sediment travels, I should plan a repeatable, safe investigation and seek permission before working on Country or Place.
Repeat each slope three times and take the middle value so the result is repeatable.
Seek permission from the land custodians, including the Traditional Owners, before investigating on Country or Place.
Pour the same amount of water from the same height every run so only the slope changes.
Choose the slope you think will win before you have measured anything.
Set the tray on a wipe-clean mat so spills do not make the floor slippery.
Decide whether each statement is evidence for the claim, or not.
Why this matters
Planning a repeatable investigation is what makes a result trustworthy. When you name the variable you change, the variable you measure and the variables you control, repeat your trials, describe the risks, set the equipment up safely, and seek the right permissions, your answer can be relied on. Scientists who study how soil and rivers move sediment plan their fieldwork in exactly this way.
Quick self-check
1. You pour water down a tray of soil to see how far sediment travels at different slopes. In a fair test, which is the variable you change?
2. In the same sediment test, which is the variable you measure?
3. Why should you repeat the test three times at each slope instead of running it once?
4. Which variables should you keep controlled (the same) every run so the test stays fair?
5. You plan to collect soil from a creek bank in bushland. What is the responsible planning step before you go?