Required practical key Words

Question 1

Sources of Error

Answer 1

Something that can cause an anomaly

Question 2

Accuracy

Answer 2

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

Question 3

Repeatability

Answer 3

The measurement is repeatable when a repetition under the same conditions gives the same or similar results

Question 4

Validity

Answer 4

How useful your evidence is to actually answer the question

Question 5

Measurement error

Answer 5

The difference between a measured value and the true value.

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. 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

Repeatable

Answer 8

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 9

Reproducible

Answer 9

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 10

Control

Answer 10

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 11

Dependent

Answer 11

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

Question 12

Independent

Answer 12

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

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

Categoric

Answer 14

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