1. Variables VARY. They are characteristics that
you need to observe, record, or measure, such as weight, height, blood lead
level, score on a test, or GPA.
2. They can be
continuous var (measurements on a sliding
scale), or categorical ('bins' or groups that whole units are placed in) such as
well/ill, exposed/not exposed, male/female, dead/alive, pre/post, etc.
variables occur before the
outcome variables, and MAY influence the outcome var. Demograophic var are always
4. Dependent var (outcome)
variables occur AFTER input var (chronologically) and may
be influenced by them.
Study of the effects of hours spent reviewing ENH440 notes on the final tern
result: INPUT (indep.) V: hours spent reviewing
(continuous), OUTCOME (dep)
V: final exam % score (continuous)
Example 2: Study of
the effects of not wearing hearing protection upon hearing damage among
riveters. Input (indep) v: wearing or not wearing protection
(categorical); Outcome (dep) v: audiometry
score % hearing loss (continuous)
Example 3: Study of
the effects of eating egg salad sandwiches on risk of illness. Input (Indep)
v: eat or not eat sandwiches (categorical);
outcome (dep) v: ill/well (categorical)
a variable be BOTH input and outcome? Yes though in separate analyses.
For instance, in a question "Does education about HIV transmission change the
knowledge of the learners about safe sex?", the Ind.var is "education", and the
Dep.var is "knowledge". But in a later analysis in the same study, you may
wish to explore the question: "do those who know about transmission of HIV
actually tend to practice safe sex?" In this case the "knowledge" is the
indep var, and the practice is the dep.var. Can you see how the
"knowledge" var changed its role here?