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Experimental design: the case for MoggyScoff
``Eight out of ten cat owners said their cats preferred MoggyScoff''
This could be interpreted in a number of different ways, e.g.,
``Eight out of ten people at the supermarket checkout with a dozen tins of
MoggyScoff in the shopping basket said their cats preferred it''
...or...
``5,000 cat owners were selected at random and forced to feed their
cats MoggyScoff for one week and Cat-o-bites for another week. Another
5,000 cat owners were forced to do the same thing, but in the opposite
order. The cat owners were watched at all times to ensure they complied with
the regime. Before starting, all ten thousand cats had electrodes implanted in
the limbic systems of their brains by which the precise amount of pleasurable
stimulation could be measured. 8,000 of the 10,000 cats showed a degree of
limbic activity with MoggyScoff that was more than two standard deviations from
the mean level of activity throughout the trial''
One of these descriptions is intuitively more convincing that the other.
Why?
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