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Accuracy An accurate measurement is one which is close to the true value.

Anomalous data Anomalous data are those measurements that fall outside the normal, or

expected, range of measured values. Variation is a characteristic of all

organisms, and it is…

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be kept constant or the investigation will not be a fair test. In some

investigations, ecological investigations in particular, it is not always

to keep confounding variables constant. In such cases, these variables

should be monitored. In this way it may be possible to decide whether
or not


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however, it might not be a causal one.

Dependent The dependent variable is the variable the value of which is measured for

variable each change in the independent variable.

Double-blind trial A trial, usually used in the context of medicine, when assessing the effects of

a new drug or treatment…

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whether to accept or reject this null hypothesis.

Placebo A placebo is a dummy pill or injection given to members of a control group

in medical trials. Where a placebo is in the form of a pill, it should be identical

to the pill used with the experimental group. The…

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Random errors

Raw data


Systematic errors

True value

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Zero errors

Probability is the likelihood of an event occurring. It differs from chance in that it can be expressed
mathematically. In statistical tests, probabilities are usually expressed as a decimal fraction of one.
Thus a probability of 0.05 means that an event is likely to occur 5 times…

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Data are only valid if the measurements that have been made are affected by a single independent
variable only. They are not valid if the investigation is flawed and control variables have been
allowed to change or there is observer bias. Conclusions are only valid if they are supported by…

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