mathematician required for simple task

In another thread I wrote

someone said it was just coincidence so I wrote

but I'm not certain now that I got the figures right - I mean my own experience is that I rarely dream of spiders and rarely see them on bed covers -
Can anyone help make this figure at least represent the true odds given the variables stated please IE: seing a spider on a bed = 1 in 20 years
dreaming of a spider perse' 1 in 5 years (never have dreamt of a spider on a bed - so ?)

 

Perhaps there really is a spider in your room, and you can only see him when you illuminate the bed by the light of the television. Or perhaps he's draw by the light given off by the television. It would be a totally random act and probably couldn't be calculated.

 

1 spider in bed in 20 years is a totaly crazy figure
i'm sure u have dozens or more every year but dont notice them
having a dream about it increases the odds that you'll notice when there is 1
the chances are that theres a spider in the bed at least once a week..1-7 chance the spider will be there 24 hours later
now lets say a spider repressents 1/100000 of the size of the bed, so is easily missed
however, having the dream about it you're far more likely to be looking for spiders in the bed..
the chances you'll notivce the spider there probly increase to a 1 in 3 chance
but thats a guess not a calculation

 

Well the odds of you dreaming about a spider only you know. The odds of a spider being on your bed are pretty high. I can't remember the last time I couldn't see evidence of a spider around if looked hard enough, infact I can see one under my desk now that id never noticed before. Theres the psychological effect that if you hadn't had the dream you'd probably have never noticed the spider.

 

I couldnt help noticing the spider it was walking up the duvet toward my head - exactly as in the dream the previous night - and to my knowledge thats probably the only time I've ever seen a spider on a bed. I can only remember dreaming of spiders a couple of times so -
Anyway the real spider did exactly as in the dream - it all happened exactly the same Its just too wierd and I would have seen it - by british spider sizes it was pretty big actually

 

Maybe you are psychic, try the pools, if you can string together a good run of wins then maybe you are onto something.

 

What can't be calculated is the number of times that you saw a spider in the bed that you didn't remember.

 

yeah but lets say those are the correct figures
so once in 1825 days you dream of spiders
and once in 7300 you see a spider on a bed
what are the chances that you would dream of a spider on the bed
and 24 hours later there is a spider on the bed?

 

Let t(0) be when a dream occures.
What is the probablity that there a spider is seen on the bed at time t(1)?
1/7300

On average, for every 7300 spider dreams one has, on one occasion the dreamer will see a spider on their bed the next day.

 

That's very simply maths...24 hours being one day...
So 1/1825 chance of you dreaming of a spider... 1/7300 chance of you Seeing a spider on a bed...on any given day the odds of them both happening is 1/13322500 or 7.5 x10 -8

VERY unlikely...but given that the actual odds of a spider being on your bed is probably much higher the figures given wouldn't be all that accurate. It's likely this is just coincidence.