In my bedroom and one other room are ceiling fans with 3 light bulbs int hem. One of the strange things I’ve always wondered about is why they didn’t all burn out at once the first time I got the fans installed and the bulbs in. Is it the way I screwed them in - some perhaps looser than others and wasting/leaking a small amount of electricity? Do some just have different levels of stuff in them than others - I wouldn’t expect that in this computerized age, but maybe.
My guess is that lightbulbs aren’t perfect machines, they have imperfections…maybe one bulb’s filament is 700 angstroms thicker or whatever and that causes the different lifespan. Or electricity irregularites feeding each individual socket.
The time it takes for a light bulb to burn out, like most things in this world, will exhibit a normal distribution.
There are naturally very small deviations in the manufacture of the filament that will affect how long the bulb lasts. Also, the number of times the bulb switched on and off, the environment in which it is kept, even the number of power surges you experience can all alter the expected life of a bulb. (A ceiling fan would cause noticeable vibration in the filament, surely shortening its life.)
So there’s an average expected life, but the realistic lifetimes of a typical sample of bulbs will be smeared across a normal (Gaussian) distribution. Most will be near the average, but there’s always a few that deviate a lot.
Again, a lot of statistical samples work this way. The distribution of IQs in people, the weights of 15-oz. boxes of Froot Loops, your bowling scores. That’s why it’s called “normal.”
Howdy, A.C.W. - welcome to SDMB! I do believe Zardoz has got it correct. And don’t worry about putting some kind of exotic bucket under that ceiling fan to catch the electricity that leaks out - that ain’t gonna happen…
audilover is correct. A Statistics 101 class will provide the answers you’re looking for.