Randi tests dowsing: 1980

[Admin]

This is a programme made by Australian TV where Randi tests dowsers: http://video.google.com/videoplay?docid=7461912885649996034

The conclusion is that dowsing doesn't work and the results back that up.

There is one anomaly however, that didn't get picked up or challenged. In the water test the dowsers had a 1 in 10 chance of guessing correctly (10 pipes - 1 with water flowing through it) so by pure guessing they should score a hit around 10% of the time.

In 50 trials the most likely outcome is that guessing at random would result in 5 hits out of 50 guesses (10%).

The dowsers in this test scored 11 hits out of 50 (22%).

That is 11/50 with a 1 in 10 chance of success. That doesn't make it twice as unlikely than getting 5/50, it makes it around 30 times more unlikely. :huh:

The actual odds of scoring 11/50 are 1 in 163. So on that test the dowsers did quite well.

That may be due to a statistical anomaly or that the test wasn't properly blinded.

They scored pure chance on the Gold dowsing and lower than chance in the Brass dowsing test.

Overall they scored 15 hits out of 111 - a result that is in accordance with pure chance.

[Blue Bubble]

Yeah, I watched it too.

To a person, the dowsers were unshaken in their belief after the results were announced (exactly as Randi predicted - he must by psychic ;) ).

On the same page, there's a link to Randi debunking Uri Geller (the Johnny Carson Show clip was ace). Well worth watching too.

[Admin]

To a person, the dowsers were unshaken in their belief after the results were announced (exactly as Randi predicted - he must by psychic ;) ).


There's a lesson in there somewhere. ;)

Testing people like this is worthwhile as it can be used to educate people. Doing it to convince believers that their belief is false however, is futile. They'll just explain away anything they don't want to see.

[tkingdoll]

I just watched the documentary, it was great. I have downloaded it to my iPod Video as my own personal portable de-bunking machine.

Randi just rocks.

[Dr B]

John

I spotted th water dowsing anomaly as well. 22% to be explained. My hunch is these field-tests are very difficult to control - some information leakage perhaps.

When in the lab proper - I think it drops back down to chance......

[Admin]

There are lots of other tests done, including the one the Australian Skeptics put up a week or so back (from 2002), which shows that dowsers fail proper tests and go into unfeasible excuse mode afterwards. ;D

Perhaps using the pipes was a bit too elaborate? The tests with the metal inside boxes is probably easier to control.