Practicals glossary

Question 1

accuracy

Answer 1

close to the true value

Question 2

calibration

Answer 2

marking a scale on a measuring instrument
(involves establishing relationship between the indications of the instrument and the values it measures, e.g. putting a thermometer in melting ice to see if it reads 0)

Question 3

data

Answer 3

qualitative or quantitative information which has been collected

Question 4

measurement error

Answer 4

difference between measured value and true value

Question 5

anomalies

Answer 5

values in a set of results which are not part of the variation caused by random uncertainty

Question 6

random error

Answer 6

causes readings to be spread about the true value due to unpredictable variations from one measurement to the next
(present with any measurement, and can’t be corrected, but the effect can be reduced by taking more measurements and calculating a new mean)

Question 7

systematic error

Answer 7

causes readings to differ a consistent amount from the true value
(sources can include environment, instruments or methods of observation and must be dealt with by repeating data collection using different technique or equipment and comparing results)

Question 8

zero error

Answer 8

when a measuring system gives a false reading when the true reading is zero

Question 9

evidence

Answer 9

data that has been shown to be valid

Question 10

fair test

Answer 10

where only the independent variable has been allowed to affect the dependent variable

Question 11

hypothesis

Answer 11

proposal intended to explain certain facts or observations

Question 12

interval

Answer 12

quantity between readings

e.g. 11 readings spaced over a distance of 1 metre would give a 10cm interval

Question 13

precision

Answer 13

where there is very little spread about the mean value

depends only on extent of random errors, does not indicate accuracy

Question 14

prediction

Answer 14

statement suggesting what will happen in future, based on observation, experience or hypothesis

Question 15

range

Answer 15

maximum and minimum values of independent or dependent variables
(e.g. from 10cm to 50cm)

Question 16

repeatable

Answer 16

when the original experimenter obtains the same results when they repeat the investigation

Question 17

reproducible

Answer 17

if the investigation is repeated by another person or by using different equipment/techniques and yields the same results

Question 18

resolution

Answer 18

the smallest change in the quantity being measured (input) that gives a perceptible change in the measuring instrument’s reading

Question 19

sketch graph

Answer 19

line graph that shows general shape of relationship between two variables
not necessarily on grid
no points plotted
axes should be labelled but may not be scaled

Question 20

true value

Answer 20

value that would be obtained in an ideal measurement

Question 21

uncertainty

Answer 21

interval within which the true value can be expected to lie

with a given level of confidence or probability e.g. the length is 20cm+-2cm at a level of confidence of 95%

Question 22

validity

Answer 22

how well the investigative procedure can answer the question being asked
(e.g. trying to find out if the rate of a chemical reaction depended on concentration of a reactant would not be a valid procedure if temperature wasn’t 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

physical, chemical or biological quantities or characteristics

Question 25

categoric variables

Answer 25

those which have values that are labels (e.g. names of plants or types of material)

Question 26

continuous variables

Answer 26

have values (quantity) that can be given magnitude by counting (e.g. number of shrimp) or measuring (e.g. light intensity)

Question 27

control variables

Answer 27

one which may affect the outcome of the investigation and therefore must be kept constant or at least monitored

Question 28

dependent variables

Answer 28

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

Question 29

independent variables

Answer 29

the variable for which values are changed or selected by the investigator

Question 30

nominal variables

Answer 30

type of categoric variable where there is no ordering of variables (e.g. red flowers, pink flowers, blue flowers)