What are dependent, independent, and extraneous (confounding) variables?

The dependent varible is defined as the thing which is being measured in an experiment, whilst the independent variable is the thing that is being manipulated or changed. Extraneous variables are undesirable variables that influence the relationship between the variables that the experimenter is observing.  For example: An experimenter was studying the effects of gender on response times, with the theory that females would be slower than males. The experimenter studied 20 participants in a public computer room throughout the day. The dependent variable is the response times, the indepdent variable is the gender of participants, and extraneous variables could be time of day or how noisy the computer room is.