The probability is not double. If p is the probability of a man under one bed, then (1-p) is the probability of no man under one bed, and (1-p)(1-p) is the probability of no man under either bed, and 1-(1-p)(1-p) is the probability of a man under either bed.
Although, this does approximate doubling for the vanishingly small probabilities we are talking about in Lucille’s case, for more measurable probabilities (or more beds), it does not. E.g. if there is a 20% chance of a man under one bed, then the chance of a man under either bed is 1-(0.8*0.8) or 36%.
This is extremely important when it comes to what is sold as “safe sex”. If your birth control / protection is 99.9% effective, but you use it 52 times in a year, it has to be effective all 52 times to be effective over all (ignoring cycles, which complicate the example but do not change the principle). The probability of all 52 times being effective is .999⁵² or 95%. After two years, the overall effectiveness is 90%.
An unexpected baby can be a blessing, but this much ignored mathematical fact is much more troublesome when it comes to alleged protection from diseases transmitted by promiscuity.
There once was a lonely old spinster / Luck for years had been ag’inst her / When a man came to burgle / She shrieked with a gurgle / “Stay there while I called in a min’ster!” – 60+ y.o. joke book
jagedlo about 5 years ago
was she expecting twins then?
jpayne4040 about 5 years ago
Even the boogeyman would be scared of her!
Sakamichi about 5 years ago
Lucille and her two mattress’s. Now there’s a “menage et trois” I definitely don’t want to see. Lol!
Dani Rice about 5 years ago
Her bedtime prayer is “Lord, have Murphy on me”.
daijoboo Premium Member about 5 years ago
Two times zero is the same as one times zero, though.
Smith Grabholz about 5 years ago
Classic, again.
stuart about 5 years ago
The probability is not double. If p is the probability of a man under one bed, then (1-p) is the probability of no man under one bed, and (1-p)(1-p) is the probability of no man under either bed, and 1-(1-p)(1-p) is the probability of a man under either bed.
Although, this does approximate doubling for the vanishingly small probabilities we are talking about in Lucille’s case, for more measurable probabilities (or more beds), it does not. E.g. if there is a 20% chance of a man under one bed, then the chance of a man under either bed is 1-(0.8*0.8) or 36%.
This is extremely important when it comes to what is sold as “safe sex”. If your birth control / protection is 99.9% effective, but you use it 52 times in a year, it has to be effective all 52 times to be effective over all (ignoring cycles, which complicate the example but do not change the principle). The probability of all 52 times being effective is .999⁵² or 95%. After two years, the overall effectiveness is 90%.
An unexpected baby can be a blessing, but this much ignored mathematical fact is much more troublesome when it comes to alleged protection from diseases transmitted by promiscuity.
kab2rb about 5 years ago
Too funny.
gcarlson about 5 years ago
There once was a lonely old spinster / Luck for years had been ag’inst her / When a man came to burgle / She shrieked with a gurgle / “Stay there while I called in a min’ster!” – 60+ y.o. joke book
davetb1956 about 5 years ago
With two beds to look under she should still want the man smart enough to sleep on top of the other bed.