57
Measurement error
Textbook: Part 2, lesson 57, pp. 57–59
GoalMeasurement error: difference between measured and true value.
New words
error · xatoliktrue value · haqiqiy qiymatmeasured value · o‘lchangan qiymatvalue of a division · bo‘linma qiymati
Explanation
No measurement is perfectly exact. The difference between the measured and the true value is the error: subtract the smaller value from the larger. If the true length is 53 mm and the measurement is 55 mm, the error is 55 − 53 = 2 mm. The error is usually not larger than the division value of the instrument: with a millimetre ruler it is up to 1 mm.
Worked examples
True 1 000 g, scale shows 985 g: error 1 000 − 985 = 15 g.
True 25 kg, measured 24 kg: error 1 kg.
Class activity
“Find the error”: measure the width of a desk twice with a ruler, compare the results and write the difference.
Practice
1
The true length is 53 mm and the measured one is 55 mm. How many mm is the error?
2
2
The true mass is 1 000 g and the scale shows 985 g. How many g is the error?
15
3
A table is 740 mm high and the measurement gave 738 mm. How many mm is the error?
2
4
A sack is truly 25 kg and the measurement gave 24 kg. How many kg is the error?
1