Practicals glossary Flashcards
accuracy
close to the true value
calibration
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)
data
qualitative or quantitative information which has been collected
measurement error
difference between measured value and true value
anomalies
values in a set of results which are not part of the variation caused by random uncertainty
random error
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)
systematic error
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)
zero error
when a measuring system gives a false reading when the true reading is zero
evidence
data that has been shown to be valid
fair test
where only the independent variable has been allowed to affect the dependent variable
hypothesis
proposal intended to explain certain facts or observations
interval
quantity between readings
e.g. 11 readings spaced over a distance of 1 metre would give a 10cm interval
precision
where there is very little spread about the mean value
depends only on extent of random errors, does not indicate accuracy
prediction
statement suggesting what will happen in future, based on observation, experience or hypothesis
range
maximum and minimum values of independent or dependent variables
(e.g. from 10cm to 50cm)
repeatable
when the original experimenter obtains the same results when they repeat the investigation
reproducible
if the investigation is repeated by another person or by using different equipment/techniques and yields the same results
resolution
the smallest change in the quantity being measured (input) that gives a perceptible change in the measuring instrument’s reading
sketch graph
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
true value
value that would be obtained in an ideal measurement
uncertainty
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%
validity
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)
valid conclusion
a conclusion supported by valid data obtained from an appropriate experimental design and based on sound reasoning
variables
physical, chemical or biological quantities or characteristics
categoric variables
those which have values that are labels (e.g. names of plants or types of material)
continuous variables
have values (quantity) that can be given magnitude by counting (e.g. number of shrimp) or measuring (e.g. light intensity)
control variables
one which may affect the outcome of the investigation and therefore must be kept constant or at least monitored
dependent variables
the variable of which the value is measured for each and every change in the dependent variable
independent variables
the variable for which values are changed or selected by the investigator
nominal variables
type of categoric variable where there is no ordering of variables (e.g. red flowers, pink flowers, blue flowers)