practical terms

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 0 °C, 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

measurement error

Answer 4

The difference between a measured value and the true value.

Question 5

anomalies

Answer 5

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

Question 6

random error

Answer 6

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 7

systematic error

Answer 7

These cause readings to differ from the true value by a consistent amount each time a
measurement is made.
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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 8

zero error

Answer 8

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.

Question 9

Evidence

Answer 9

Data that have been shown to be valid.

Question 10

Fair test

Answer 10

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

Question 11

Hypothesis

Answer 11

A proposal intended to explain certain facts or observations.

Question 12

Interval

Answer 12

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 13

Precision

Answer 13

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 14

Prediction

Answer 14

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

Question 15

Range

Answer 15

The maximum and minimum values of the independent or dependent variables.
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 16

Repeatable

Answer 16

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

Question 17

Reproducible

Answer 17

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 18

Resolution

Answer 18

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

Question 19

Sketch graph

Answer 19

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 20

True value

Answer 20

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

Question 21

Uncertainty

Answer 21

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 22

Validity

Answer 22

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 23

Valid conclusion

Answer 23

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

Question 24

Variables

Answer 24

These are physical, chemical or biological quantities or characteristics.

Question 25

categoric variables

Answer 25

Categoric variables have values that are labels eg names of plants or types of material or
reading at week 1, reading at week 2 etc.

Question 26

continuous variables

Answer 26

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).

Question 27

control variables

Answer 27

A 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 28

dependent variables

Answer 28

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

Question 29

independent variables

Answer 29

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

Question 30

nominal variables

Answer 30

A nominal variable is a type of categoric variable where there is no ordering of categories (eg
red flowers, pink flowers, blue flowers)