Hmm my water pump failed again!!!! Could it be the pulley?!?!

[fmicle]

Originally Posted by Tamago

the ratio of water pump failures stock vs pulley tells the tale..

I beg to differ. This is a typical mistake people make, just because there is a correlation between A and B it doesn't mean A caused B or vice versa.

Let me explain with an example: studies show that households with more books have smarter kids (correlation between books and kids), so a mayor in Illinois thought he'll simply give away free books and make kids smarter. Needless to say, the plan didn't work. Because it's not the number of books that cause the kids to be smart, it's their parents' education, status, emphasis on school, etc. And those families are likely to have more books to begin with. So, there is another parameter C that causes both A and B to go together.

Back to our situation: people with aftermarket pulleys have more water pump failures than the ones driving stock (that's the correlation). So some people incorrectly infer that the pulleys must cause the failure.

Imagine this: people who install aftermarket parts and tune their cars are more likely to drive their cars more aggressively, therefore putting more stress on their parts than those driving stock (grandma, grandpa, uncle Jimmy).

Just remember the basic principle: correlation does not imply causation. For more details check it out on Wikipedia: Correlation does not imply causation

[PHXDEMON]

Originally Posted by fmicle

I beg to differ. This is a typical mistake people make, just because there is a correlation between A and B it doesn't mean A caused B or vice versa.

Let me explain with an example: studies show that households with more books have smarter kids (correlation between books and kids), so a mayor in Illinois thought he'll simply give away free books and make kids smarter. Needless to say, the plan didn't work. Because it's not the number of books that cause the kids to be smart, it's their parents' education, status, emphasis on school, etc. And those families are likely to have more books to begin with. So, there is another parameter C that causes both A and B to go together.

Back to our situation: people with aftermarket pulleys have more water pump failures than the ones driving stock (that's the correlation). So some people incorrectly infer that the pulleys must cause the failure.

Imagine this: people who install aftermarket parts and tune their cars are more likely to drive their cars more aggressively, therefore putting more stress on their parts than those driving stock (grandma, grandpa, uncle Jimmy).

Just remember the basic principle: correlation does not imply causation. For more details check it out on Wikipedia: Correlation does not imply causation

Wisdom