Glossary

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 quality values, which must be applied. For example, placing a thermometer in melting ice to see whether it reads zero in order to check that it is calibrated correctly.

Question 3

Data

Answer 3

Information, either qualitative or quantitive, that has been collected.

Question 4

Error

Answer 4

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, e.g the needle on an ammeter failing to return to zero when no current flows. A zero error May result in systematic uncertainty.

Question 10

Evidence

Answer 10

Data which has 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, e.g 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 mean value. Precision depends only on the extent of random errors.

Question 15

Prediction

Answer 15

A statement suggesting what will happen in the future, based on observation, experience or a hypothesis.

Question 16

Range

Answer 16

The maximum and minimum values of the independent or dependent variables; important in ensuring that any pattern is detected. For example, a range of distances may be quoted as either: From 10cm to 50cm or from 50cm to 10cm.

Question 17

Repeatable

Answer 17

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

Question 18

Reproducible

Answer 18

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

Question 19

Resolution

Answer 19

Smallest change in the quantity being measured of a measuring instrument that gives a perceptible change in the reading.

Question 20

Sketch graph

Answer 20

A line graph, not necessarily on a grid, that shows the general shape of the relationship between two variables. It will not have any points plotted and although the axes should be labelled they may not be scaled.

Question 21

True value

Answer 21

This is the value that would be obtained in an ideal measurement.

Question 22

Uncertainty

Answer 22

The interval within which the true value can be expected to lie. Whenever a measurement is made, there will always be some uncertainty or doubt about the result obtained. Uncertainty can be expressed in terms of spread of values obtained.

Question 23

Validity

Answer 23

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 24

Valid conclusion

Answer 24

A conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning.

Question 25

Variables

Answer 25

Physical, chemical or biological quantities or characteristics

Question 26

Categoric

Answer 26

Values that are labels e.g names of plants

Question 27

Continuous

Answer 27

Can have values that can be given a magnitude either by counting or by measurement

Question 28

Control

Answer 28

One which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or monitored

Question 29

Dependent

Answer 29

Value measured for each and every change of the independent variable

Question 30

Independent

Answer 30

Variable for which values are changed or selected by the investigator.