lesson
Repeated measurements do not remove every error
1 · Learn
Repeating a measurement can reveal variation and support an estimate of a mean. A consistently miscalibrated instrument can still give similar but inaccurate readings. Repeatability and accuracy are related to different questions.
Record units, resolution and conditions. Do not delete an unusual result solely to improve agreement; investigate and document a reason before excluding it.
2 · Worked example
Readings 10.1, 10.2 and 10.1 are close together, but a zero error of +1.0 would shift all of them. Their closeness alone does not establish accuracy.
3 · Your turn
Why can repeated readings all agree yet all be too high?
Check your answer
A systematic error, such as an instrument zero error, can affect every reading similarly.
4 · Apply your learning
Use invented readings to compare spread and possible bias, without presenting them as measured experimental evidence.
Adult guidance and safety
Use supplied evidence and approved models. Practical science needs a qualified adult, appropriate equipment and a risk assessment. Do not attempt chemical reactions, heating, mains electricity or solar observation independently. Never request personal health or genetic disclosures.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
My observation notebook
Follow your teacher's approved method and safety instructions. Record the sample or supplied dataset, conditions, measurements with units and uncertainties where appropriate. Distinguish observations from explanations. A described experiment is not permission to carry it out; do not improvise equipment or invent missing results.
Ask your teacher for support with the method and recording. A prediction is what you think might happen; an observation is what you actually see, hear or feel safely.
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