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(synonym: factor, outcome) – A variable is a factor you measure, such as pain, depression, disability, CRP. Different variables are measured in different ways for example:
Dichotomous or ‘yes/no’ answers (e.g. alive or dead)
Continuous measurements (e.g. length can be 61cm or 61.25 cm or 61.257 cm)
Discrete measures have to be whole numbers (e.g. number of children cannot be 1.6!)
Categories such as blue or green, no pain or some pain
Variables can also be labelled as:
Primary – the main question the study is asking (e.g. change in pain)
Secondary – the next question you would like to ask (e.g. change in disability)
Clinical – health status, e.g. pain, disability
Demographic – details such as age, gender, education level
Confounding – variables which might confuse your answer; e.g. there seems to be an association between alcohol and lung cancer. But this does not mean alcohol causes lung cancer. The link is really between smoking and lung cancer – alcohol confounds or confuses the issue because people who drink alcohol are more likely to smoke and therefore get lung cancer

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