Scary Lampposts

[fluffymark]

Maybe it's just me. Or maybe they really don't like me. I was walking under the lamppost at the end of my street on my way home just now, and just as I passed underneath - *pow* - it goes out. Now it could be a coincidence, but it's happened few times before with that lamppost, and I'm beginning to think it hates me. There was also a similar lamppost on Jesus Lane in Cambridge that was worse - I could guarantee turning off that lamppost just by walking underneath it. Every time - *pow* - it went out. Anyone have any clues why this happens? *paranoid*

Aside from the scary lamppost business I've had a fun evening out. At 5pm I escaped form the office and walked to the perfume shop in aldgate where Doseybat now works, and it's really nice there - I'd even find genuine reasons to shop there. Yay! At 6 she got off work and we both headed to the Virgin Megastore to find Tristan and Mandy who were watching the Von Bondies play there, but they weren't letting anyone else in (meanies!), so we had to wait. Eventually, got to meet Mandy again (it's been years! Ack!) but only briefly. I then headed to the Intrepid fox for free food and an Emily. Yay! :)

*very* tired now. Time for beddy byes. zzzzzzzzz

Comments

scary lampposts and other bizarre coincidences

[(Anonymous)]

Everyone does this sort of coincidence spotting. It's because you only notice the times it does happen, you don't remember the times when it doesn't. Also, once you've noticed it happening once, next time you'll see it flicker out for a bit when you're half way down the street and think you did that. Like the way pessimistic people will tell you it's rained the whole summer, whilst I'll say it's been great weather and I've got the sunburn and the scars from falling down on concrete to prove it, whereas if you look at it, it probably rained a bit, but no more than usual, it just depends on which events you remember most.

Also, after a bit of thinking about probability it becomes obvious that one in a million chances happen all the time. For example it's probably a one in a million chance that my plant would have got blown off my desk at work by my fan, but it happened. It's pretty much inevitable that some incredibly unlikely event (such as lights going out) will happen to you, which you'll remember, whereas millions of other unlikely events won't have happened, but you won't know about any of them.

In naughty maths speak you've got P(event) = not very much, but for a pretty much infinite number of improbable events, P( event1 OR event2 OR event.....) is pretty close to 1 isn't it?

Given I'm in full on maths head mode and I'm well bored at work and cos I'm trying to get my cleverness back in case I need it to get a new job, here's the scary maths which I think is probably right but I'm not sure.

assuming each possible event Xn has the same (very small) probability - this is just a simplification, if you take this to be the minimum probability for all your events, you'll get a final probability that is equal to or less than the actual probability.

P(Xn) = p

P( X1 | X2 | ...|Xn ) = P[n]

P(!X1) * P[n-1] + P(X1)

= p + (1-p) * P[n-1]

P[1] = p

p + (1-p)p + (1-p)(1-p)p + ((1-p)^n)p

which if you have a large number for n always tends to 1

eg. if you've got 1000 events with a probability of 1 in a million, you've got a chance of 0.9995 that one of them will happen.

guess who.

Re: scary lampposts and other bizarre coincidences

[fluffymark]

Hmmm i'm trying to think would post anonymous maths all over my livejournal. *laughs* Actually I know far too many people who may do that.

I get your point -however for the sake of correctness i'd like to make a few alterations to your calculations. Your algebra is fine, just your numbers.

1000 events with a probability of 1 in a million still only has a probability of about 1 in 1000 (actually just under) that one will happen. Think about it.

1 million events with a probability of 1 in a million has a probability of 0.63212..... [for large n, this tends to 1-(e^-1)] that one of them will happen. Heaps better, but still not close to unity.

But thats me being pedantic. Given significantly more than a million events, it's fairly close to unity that a one in a million event will occur. True.

This still doesn't explain the lamppost. It only happens with certain lampposts. And it happens with the same ones. The one on jesus lane in cambridge went *pow* and went out every time i stepped under it. I've had witnesses confirm this. The chances of that happening at random are so small compared to the number of lampposts i've walked under in my life that it cannot be due to just probabilistic effects.

Now, can we stop talking about maths, please? :)

Re: scary lampposts and other bizarre coincidences

[alektoeumenides.livejournal.com]

I take a guess that it is a certain Mr J. Marshall.

Shut up you blonde bimbo ;) Quitit with these maths. Us humanities students just can't cope with all of that claptrap.

Re: scary lampposts and other bizarre coincidences

[fluffymark]

'falling on concrete' - i think you're right val - only one person i know rides a unicycle and then also uses phrases like 'naughty maths'.

*waves to joe* :) How often do you read my little gossip column here?

(maybe see you at oscar's thing tomorrow?)