Key Words

Question 1

Accuracy

Answer 1

A measurement result is considered accurate if it is judged to be close to the true value.

Question 2

Calibration

Answer 2

Marking a scale on a measuring instrument. This involves establishing the relationship between indications of a measuring instrument and standard or reference quantity values, which must be applied. For example, placing a thermometer in melting ice to see whether it reads zero, in order to check if it has been calibrated correctly.

Question 3

Data information

Answer 3

either qualitative or quantitative, that has been collected.

Question 4

Error

Answer 4

See also uncertainty.

Question 5

Measurement error

Answer 5

The difference between a measured value and the true value.

Question 6

Anomalies

Answer 6

These are values in a set of results which are judged not to be part of the variation caused by random uncertainty.

Question 7

Random error

Answer 7

These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next. Random errors are present when any measurement is made, and cannot be corrected. The effect of random errors can be reduced by making more measurements and calculating a new mean.

Question 8

Systematic error

Answer 8

These cause readings to differ from the true value by a consistent amount each time a measurement is made. Sources of systematic error can include the environment, methods of observation or instruments used. Systematic errors cannot be dealt with by simple repeats. If a systematic error is suspected, the data collection should be repeated using a different technique or a different set of equipment, and the results compared.

Question 9

Zero error

Answer 9

Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero, eg the needle on an ammeter failing to return to zero when no current flows. A zero error may result in a systematic uncertainty.

Question 10

Data

Answer 10

Data which has been shown to be valid.

Question 11

Fair test

Answer 11

A fair test is one in which only the independent variable has been allowed to affect the dependent variable.

Question 12

Hypothesis

Answer 12

A proposal intended to explain certain facts or observations.

Question 13

Interval

Answer 13

The quantity between readings, eg a set of 11 readings equally spaced over a distance of 1 metre would give an interval of 10 centimetres.

Question 14

Precision

Answer 14

Precise measurements are ones in which there is very little spread about the

Question 15

Accuracy

Answer 15

A measurement result is considered accurate if it is judged to be close to the true value.

Question 16

Uncertainty

Answer 16

Uncertainty The interval within which the true value can be expected to lie, with a given level of confidence or probability, eg ‘the temperature is 20 °C ± 2 °C, at a level of confidence of 95%’.

Question 17

Resolution

Answer 17

This is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading.

Question 18

Repeatable

Answer 18

A measurement is repeatable if the original experimenter repeats the investigation using same method and equipment and obtains the same results. Previously known as reliable.

Question 19

Reproducible

Answer 19

A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained. Previously known as reliable.

Question 20

Validity

Answer 20

Suitability of the investigative procedure to answer the question being asked. For example, an investigation to find out if the rate of a chemical reaction depended upon the concentration of one of the reactants would not be a valid procedure if the temperature of the reactants was not controlled.

Question 21

Precision

Answer 21

Precise measurements are ones in which there is very little spread about the mean value. Precision depends only on the extent of random errors – it gives no indication of how close results are to the true value.

Question 22

Random error

Answer 22

an error in measurement caused by factors which vary from one measurement to another.

Question 23

Systematic error

Answer 23

an error having a non-zero mean, so that its effect is not reduced when observations are averaged.

Question 24

Anomaly

Answer 24

something that deviates from what is standard, normal, or expected.

Question 25

Accuracy

Answer 25

of a measurement system is the degree of closeness of measurements of a quantity to that quantity’s true value.

Question 26

Precision

Answer 26

Precise measurements are ones in which there is very little spread about the mean value

Question 27

Repeatable

Answer 27

A measurement is repeatable if the original experimenter repeats the investigation using same method and equipment and obtains the same results.

Question 28

Reproducible

Answer 28

A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.

Question 29

Uncertainty

Answer 29

means the range of possible values within which the true value of the measurement lies.