To design a good experiment, an investigator must consider all variables that might affect the outcome. What is a variable?
A variable in an experiment is a quantity or an attribute whose value may vary over the course of an experiment. There are independent and dependent variables. The independent variable is the one being manipulated by an experimenter
. The dependent variable is the the variable upon which the effects of manipulating the independent variable are seen/observed.
- Independent variable - number of daily calories
- Dependent variable - weight
In an experiment, one may wish to examine the effect of the number of daily calories on weight. Therefore, the experimenter (you) would manipulate the number of daily calories and see the change in weight over the course of weeks/months/years