- VARIABLES:
Any quantity that varies is called a variable.
If at all possible, it helps to identify one variable as the "independent variable" and the other as the "dependent variable."
By custom, the independent variable is plotted horizontally, on the X-axis. The dependent variable is plotted vertically, on the Y-axis.
- Which is which? Obvious cases:
1. If you know that one variable is (or could be) the cause, and the other is (or could be) the effect, then the cause is the
independent variable
and the effect is the dependent variable because it depends on the cause.
Ask yourself: would it make sense to switch them the other way around?
2. If a scientist controls one variable in an experiment (like how much of some food or nutrient) and measures the outcome that he or she
doesn't control
(like weight gain), then the independent variable is the one that was controlled and the outcome
is the dependent variable.
3. Time is nearly always the independent variable. It usually means "time since my observations began."
- Occasionally, both variables are dependent because neither can possibly influence the other. In that case,
the choice of which to call X and which to call Y is arbitrary.
- Remember:
By custom, the independent variable is plotted horizontally, on the X-axis. The dependent variable is plotted vertically, on the Y-axis.
|