Split a bottle of sink de-clogger between 4 glasses, and cut a steak into bite sized chunks and split between 4 bags.
i) Empty 1 bag into a glass.
ii) Hit 1 bag with a tenderiser 10 times before emptying it into a glass.
iii) Hit 1 bag with a tenderiser 30 times before emptying it into a glass.
vi) Hit 1 bag with a tenderiser 50 times before emptying it into a glass.
After 4 hours sieve and weigh the remaining solids.
i) Lots left.
ii) Some left.
iii) Little left.
iv) Not too different from iii)
2) Hypothesis: People can't divine for metal.
Stolen from Dawkins.
Experimenter 1 places a metal object under a small fraction of a number of buckets, records this, and leaves.
Experimenter 2, without meeting Experimenter 1 leads the diviner into the room, and lets them test each bucket with divining sticks, and records the result.
The experimenters results are compared.
The number of buckets whose contents are correctly identified is not significantly higher than would be expected if the selection was at random (this number to be determined before the experiment starts).
cDave should do these (and more):