Extraneous and confounding variables

[IvanJames]

Hey, so if a question asked "What is the main difference between extraneous and confounding variables?"

What would be an appropriate answer to that?

[slothpomba]

[Note i haven't taken VCE Psych and i dont know if this matches what you need to know]

A confounding association is one that does not have a cause-effect relationship. An epidemology professor told us about a famous association between lung cancer and heavy drinking. Heavy drinking is highly correlated with lung cancer. It's not that lung cancer is caused by drinking. What is it then? Turns out heavy drinkers also tend to be heavy smokers and THIS is what is linked to the lung cancer. There are plenty of examples out there on the net.

Basically its an association thats not necessarily a causation.

[mishamigo]

An extraneous variable is a variable other than the IV that could cause changes in the value of the DV. Extraneous variables are undesirable. When the potential effects of an extraneous variable have been removed from the experiment (usually by the experimental design), the variable is said to be a controlled variable.
A confounding variable is a variable other than the IV that has a systematic effect on the value of the DV. If a confounding variable exists, the research is usually a waste of time and no valid conclusions can be drawn, so very stringent procedures are used to prevent this happening.

Basically: extraneous MAY cause changes, confounding DOES cause changes.