There are two main ideas that students need to understand about fair testing:
1. In a fair test scientific investigation variables need to be carefully managed so that you: change one thing, measure one thing and keep all other things the same = Change, Measure, Same
2. Investigations need to be repeated to increase the likelihood of the results being reliable. Generally each measurement should be taken several times (e.g. 5 times and then averaged) and measured as accurately as possible.
In investigation A above test at least 5 different fibres of the same material and of the same length.
Living things have a lot of inbuilt variation to how they naturally behave, grow etc. So, when testing the growth of seedlings (investigation C above) many e.g. 30 wheat seeds need to be grown in each type of soil. Every 2-3 days students could then measure the two smallest, the 2 middle size and the 2 tallest seedlings in each soil type and average the results.
Learning the steps in the scientific process
Posters reminding students about the steps in the scientific process could be displayed in the classroom.
Click here to download: Cows Moo Softly (186.26 kB)
Click here to download: Steps In The Scientific Process (13.85 kB)
Selecting Practice Investigations
Try to select investigations that relate to the class theme.
Here are some suggestions for simple investigations that will allow you and your students to practice the steps of the scientific process.
GEMS â€“ simple investigations
1. Soil as a water filter â€“ which soil combination is best?
- sand alone
- soil alone
- sand with soil on top
- soil with sand on top
Change = type of soil
Measure = clarity of water
Same = total amount of 'filtering agents' + size and type of filter + amount and type of dirty water
The website Dr Dirt provides a range of teaching resources on soil including a hands on investigation on soil as a filter.
2. Windmill investigations â€“ which is the best design for maximizing the number of turns?
- number of blades
- shape of blades
- length of blades
- material of blades
Change = ONE design feature of windmill
Measure = number of turns per minute
Same = length of 'stem' + amount of wind, direction of wind (use a fan) + all other design features
3. Using the sun to heat water â€“ What affects the rate that water heats up?
- colour of water
- colour of container
- material of container
- shape of container
Change = ONE design feature of above
Measure = temperature increase of water over time
Same = amount of water + amount and direction of sunlight + all other design features
Use this short quiz to test your knowledge of what is a fair test