Two examples of lurking variables are the color of a paper airplane and its ability to fly and the size of the thymus in children who developed SIDS in the early 1900s. Neither of the two factors are responsible for either effect. A lurking variable is an extraneous variable that does not play a role in determining the relationship between the independent and the dependent variable.
A variable is any factor that can be controlled, changed or measured in an experiment. There are several types of variables used to report the data collected from an experiment. The most-common types of variables are the independent, dependent, controlled and extraneous variables.
The independent variable is the variable or condition that the experimenter changes and controls during the experiment. The dependent variable is what is measured or obtained during the experiment. It is dependent upon the independent variable and its varying states. A controlled variable is a constant variable that does not change during an experiment.
Extraneous variables are variables that are considered extra in an experiment. They may influence the outcome of the experiment, but they aren't always taken into serious account. A lurking variable is one example of an extraneous variable.