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Scientists aim towards designing experiments that can give a “true value” from their measurements, but due to the limited precision in measuring devices, they often quote their results with some form of uncertainty.
Nature of science:
Uncertainties: “All scientific knowledge is uncertain… if you have made up your mind already, you might not solve it. When the scientist tells you he does not know the answer, he is an ignorant man. When he tells you he has a hunch about how it is going to work, he is uncertain about it. When he is pretty sure of how it is going to work, and he tells you, ‘This is the way it’s going to work, I’ll bet,’ he still is in some doubt. And it is of paramount importance, in order to make progress, that we recognize this ignorance and this doubt. Because we have the doubt, we then propose looking in new directions for new ideas.” (3.4)
Feynman, Richard P. 1998. The Meaning of It All: Thoughts of a Citizen-Scientist. Reading, Massachusetts, USA. Perseus. P 13.
Understandings:
Random and systematic errors
Absolute, fractional and percentage uncertainties
Error bars
Uncertainty of gradient and intercepts
Applications and skills:
Explaining how random and systematic errors can be identified and reduced
Collecting data that include absolute and/or fractional uncertainties and stating these as an uncertainty range (expressed as: best estimate ± uncertainty range)
Propagating uncertainties through calculations involving addition, subtraction, multiplication, division and raising to a power
Determining the uncertainty in gradients and intercepts
Guidance:
Analysis of uncertainties will not be expected for trigonometric or logarithmic functions in examinations
Further guidance on how uncertainties, error bars and lines of best fit are used in examinations can be found in the Teacher support material
Data booklet reference:
Big Questions about Uncertainty and Error
When can you use the word 'exactly'?
Theory of knowledge:
“One aim of the physical sciences has been to give an exact picture of the material world. One achievement of physics in the twentieth century has been to prove that this aim is unattainable.” – Jacob Bronowski. Can scientists ever be truly certain of their discoveries?
Utilization:
Students studying more than one group 4 subject will be able to use these skills across all subjects
Aims:
Aim 4: it is important that students see scientific errors and uncertainties not only as the range of possible answers but as an integral part of the scientific process
Aim 9: the process of using uncertainties in classical physics can be compared to the view of uncertainties in modern (and particularly quantum) physics
Resources
Resources
physics-01.4-uncertainty-complete.pdfphysics-01.5-uncertainty-in-calculations-complete.pdfUncertainties Visualized
Uncertainties Visualized
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