QTRA... V.T.A..... Or Lantra Pro tree inspection

[Amelanchier]

For instance (and obviously just as a thought exercise): if you have 10,000 trees and each of them have at least a 1:10,000 chance of killing someone over the next year, what is the chance that at least one of them will kill someone over the next year?

 

Presumably, your point is based upon the cumulative probability being more likely than the individual probability. Much in the same way as rolling more dice gives a better probability of obtaining at least one six.

 

The thing is, the target is not going to be within falling distance of all 10,000 trees at once...

[Tony Croft aka hamadryad]

You just gotta love them variables, incalcable, like I said!

[Stephen Blair]

heads or tales is a 50/50 chance of either of them landing face up, it doesnt matter how many times you do it, each time it is a 50/50 chance. This is why the casino wins and the punter looses.

[arb culture]

Tony - you're right it is about cumulative risks.

 

It is a thought excercise exploring the maths though. Let's assume that the target will be replaced by another target if the first one is destroyed/killed. Or that the target is spread over many people wjo visit infrequently and that the death of one person will not affect the numbers of visitors to the site.

[Amelanchier]

You just gotta love them variables, incalcable, like I said!

 

No it isn't.

 

You can survey the average density of trees per hectare, and determine the speed at which the average target walks along a particular footpath. You can then for any given moment work out the number of trees within falling distance (perhaps two tree heights) of the path that present a hazard and the average exposure time to the average tree.

 

Sometimes - its just not worth it though.

[arb culture]

Tony - are you are QTRA licensed user?

[Albedo]

zero .

[Tony Croft aka hamadryad]

No it isn't.

 

You can survey the average density of trees per hectare, and determine the speed at which the average target walks along a particular footpath. You can then for any given moment work out the number of trees within falling distance (perhaps two tree heights) of the path that present a hazard and the average exposure time to the average tree.

 

Sometimes - its just not worth it though.

 

but how many poeple walk there on a gusty day? on a wet and windy day?

 

one day is different to the next in all terms, number of walkers etc etc etc.

 

I think this is a nightmare calculator scenario, but i am listening, but i will take some convincing that statistics are valid

[Amelanchier]

Tony - you're right it is about cumulative risks.

 

It is a thought excercise exploring the maths though. Let's assume that the target will be replaced by another target if the first one is destroyed/killed. Or that the target is spread over many people wjo visit infrequently and that the death of one person will not affect the numbers of visitors to the site.

 

Well lets make the numbers more accessible then (slightly). Lets use 10 trees planted in a circle with a risk of 1/10 (they are uber-fubar) with an imaginary war memorial in the centre (fairly static unless a group of students spots it).

 

So is the cumulative risk to the memorial greater than the individual risk of 1/10? So we need to work out what the cumulative likihood of the event is, one way of doing it is to multiply the odds of it not happening

 

9/10 x 9/10 x 9/10 x 9/10 x 9/10 x 9/10 x 9/10 x 9/10 x 9/10 x 9/10 =

 

3,486,784,401 / 10,000,000,000 of no damage to the memorial, or;

 

6,513,215,599 / 10,000,000,000 of damage to the memorial which =

 

1:1.53 which is certainly less that 1/10 but not quite 1/1.

[arb culture]

spot on:thumbup:

 

Are you a QTRA user?