Measuring well: repeats, anomalies and reliability
A single reading is a rumour. Repeats, sensible instruments and honest handling of odd results are what turn measurements into evidence.
Part of your national curriculum
- Working scientifically: Make and record observations and measurements using a range of methods, and evaluate the reliability of methods
Lesson overview
What you'll learn in this lesson
Make and record observations and measurements using a range of methods, and evaluate the reliability of methods
Key learning points
- • Choosing the instrument
- • Repeats and means
- • Reliability and validity
This lesson at a glance
- 25 minutes
- 19 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 19
Visual introductionPicture this
Measuring well: repeats, anomalies and reliability
A single reading is a rumour. Repeats, sensible instruments and honest handling of odd results are what turn measurements into evidence.
In a nutshell
Make and record observations and measurements using a range of methods, and evaluate the reliability of methods
Learning cycle
Part 2 of 19
Learning cycle 1 of 2
Part 1 · Choosing the instrument
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 19
Learn
Choosing the instrument
Match the instrument to the size of the quantity and read to its resolution. A ruler marked in millimetres cannot honestly report 12.34 cm. Read at eye level to avoid parallax, and zero a balance before use.
Reset break
Part 4 of 19
Pause
That's sitting 1 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 19
Learn
Repeats and means
Take at least three readings for each value. Calculate a mean, but exclude any anomaly first — a result that clearly does not fit the pattern — and say in your write-up that you excluded it and why.
Quick check
Part 6 of 19
Quick check
Part 7 of 19
Reset break
Part 8 of 19
Pause
That's sitting 2 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 19
Learning cycle 2 of 2
Part 2 · Reliability and validity
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 19
Learn
Reliability and validity
Reliable means repeating the method gives similar results. Valid means the method actually tests the question, with only the independent variable changed. A method can be reliable and still invalid if a control variable was left free to change.
Quick check
Part 11 of 19
Reset break
Part 12 of 19
Pause
That's sitting 3 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 13 of 19
Explore the idea
Part 14 of 19
Worked example
Worked example: handling an anomaly
Readings: 4.2 s, 4.3 s, 7.9 s, 4.1 s. The 7.9 s value is an anomaly — probably a late stop of the timer. Mean of the remaining three is 4.2 s. Including the anomaly would have given 5.1 s, a value no single careful measurement supports.
Challenge round
Part 15 of 19
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Reset break
Part 16 of 19
Pause
That's sitting 4 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 17 of 19
Game · Recall cards
What does repeating an experiment and averaging help reduce?
Card 1 of 4
Mastery quiz
Part 18 of 19
Marked quiz
End of lesson quiz: Measuring well: repeats, anomalies and reliability
4 questions, marked with the reasoning shown. No timer.
1. What does repeating an experiment and averaging help reduce?
2. An anomalous result is one that is:
3. A method is reliable if:
4. Random error is reduced by
Lesson round-up
Part 19 of 19
Lesson round-up
Ready when you are
Quiz score
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Best run
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Ask LunaPart 1 of 19 · Watch & discover
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Make and record observations and measurements using a range of methods, and evaluate the reliability of methods