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
- 15 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 15
Watch first
Measuring well: repeats, anomalies and reliability
An English teaching video on this topic from Smart Learning Ltd. Watch it, then scroll down for the lesson.
Do it for real
The practicals below use what the film shows, with a full method you can follow at home.
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 15
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 15
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.
Explore the idea
Part 4 of 15
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 5 of 15
Quick check
Why take repeat readings?
Quick check
Part 6 of 15
Quick check
What should you do with a clear anomaly?
Reset break
Part 7 of 15
Pause
That's sitting 1 of 2 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 8 of 15
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 9 of 15
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 10 of 15
Quick check
What does a reliable method mean?
Quick check
Part 11 of 15
Quick check
Which error does reading at eye level avoid?
Explore the idea
Part 12 of 15
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 13 of 15
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
Mastery quiz
Part 14 of 15
Marked quiz
End of lesson quiz: Measuring well: repeats, anomalies and reliability
4 questions, marked with the reasoning shown. No timer.
1. Why take repeat readings?
2. What should you do with a clear anomaly?
3. What does a reliable method mean?
4. Which error does reading at eye level avoid?
Lesson round-up
Part 15 of 15
Lesson round-up
Ready when you are
Quiz score
Not sat
Games
Not played
Points this lesson
0
Best run
0 in a row
Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo the work
Your written work for this lesson
This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.
Why the school greenhouse failed
A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.
The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.
The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.
Written for Good Learning Co.
Reading questions
- Name the variable the club changed the second time, and one variable they kept the same.
- Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
- Write a conclusion for the club's report, saying how far the evidence supports it.
Method and results
WritingWrite the aim, what you changed, what you measured and what you kept the same, then record your results in a table.
1 page + results table
Conclusion
WritingExplain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.
6–8 sentences
Labelled diagram
DiagramDraw the apparatus or the process in pencil, label it fully, and photograph it.
1 labelled diagram
Reading and notes
ReadingRead the lesson text again and write the key ideas in your own words.
Half a page of notes
Saved as you type.
Part 1 of 15 · Watch & discover
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Make and record observations and measurements using a range of methods, and evaluate the reliability of methods