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

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

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 spaces over a distance of 1m would give an interval of 10 cm

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 measurements 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

This is the value that would be obtained i 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 variable

Answer 26

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

Question 27

Continuous variable

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). Previouslv known as discrete variable.

Question 28

Control variable

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 variable

Answer 29

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

Question 30

Independent variable

Answer 30

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