Is this a complete sentence?
Mr. Arnold has a long mustache it needs a trim.

Psychologists studying infant memory want to determine at what age babies can remember specific events. an experimenter uses several puppets to demonstrate a series of actions while the infant watches. after a delay, the experimenter records how many of the actions the child imitates when playing with the puppets. what is the dependent variable?

Experiment to investigate effect of medication on levels of stress in males and females. dependant variable?

An refers to a specific factor that has a range of possible values