Keywords

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

Answer 3

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

Question 4

Error

Answer 4

See also uncertainty

Question 5

Measurment error

Answer 5

The difference between a measured value and the true value.

Question 6

Anomalies

Answer 6

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

Evidence

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 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 15

Prediction

Answer 15

A prediction is 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 10 cm to 50 cm’ or ‘From 50 cm to 10 cm’.

Question 17

Repeatable

Answer 17

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 18

Reproducible

Answer 18

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 19

Resolution

Answer 19

This is the smallest change in the quantity being measured (input) 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

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. For example, a length of 56 cm ±2 cm would mean the true value could be anywhere between 54 cm and 58 cm.

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

These are physical, chemical or biological quantities or characteristics.

Question 26

Categoric

Answer 26

Categoric variables have values that are labels, eg names of plants or types of material.

Question 27

Continuous

Answer 27

Continuous variables can have values (called a quantity) that can be given a magnitude either by counting (as in the case of the number of shrimp) or by measurement (eg light intensity, flow rate etc). Previously known as discrete variable.

Question 28

Control

Answer 28

Control variable is one which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored.

Question 29

Dependent

Answer 29

Dependent variable is the variable of which the value is measured for each and every change in the independent variable.

Question 30

Independent

Answer 30

Independent variable is the variable for which values are changed or selected by the investigator.