# The Naked Scientists Forum

### Author Topic: What is the probability of 5 presidents out of 43 being left handed?  (Read 2614 times)

#### Pumblechook

• Hero Member
• Posts: 569
##### What is the probability of 5 presidents out of 43 being left handed?
« on: 25/10/2008 18:33:19 »
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4 out of 5 recent US Presidents have been left handers? Given that 1 in 10 of the population is left handed what is the probability of this? Say it was taking socks out of draw with the light off.. 1 White to 9 Black. What are chances of having 4 White and 1 Black.. I get 0.00045 ??

More accurately what is the probability that a continuous sequence of 5 presidents out of 43 has 4 left handers?

Mod edit - Formatted the subject as a question - please do this to help keep the forum tidy and easy to navigate - thanks!
« Last Edit: 28/10/2008 10:46:04 by BenV »

#### lyner

• Guest
##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #1 on: 25/10/2008 19:02:46 »
In such a small population, there is no statistical significance in whatever they turn out to be.
Don't lose faith in statistics - just use them properly.

#### Pumblechook

• Hero Member
• Posts: 569
##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #2 on: 25/10/2008 19:31:34 »
That makes no sense?

#### Bored chemist

• Neilep Level Member
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##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #3 on: 25/10/2008 20:30:33 »
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4 out of 5 recent US Presidents have been left handers? Given that 1 in 10 of the population is left handed what is the probability of this? Say it was taking socks out of draw with the light off.. 1 White to 9 Black. What are chances of having 4 White and 1 Black.. I get 0.00045 ??

More accurately what is the probability that a continuous sequence of 5 presidents out of 43 has 4 left handers?
The probbility is 100% because they do.

#### Pumblechook

• Hero Member
• Posts: 569
##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #4 on: 25/10/2008 20:35:01 »
I thought I would find some mathematicians here.

OK.  If you pulled out 10 socks from draw in the dark where the ratio of Black to White is 9 to 1 what is the probability of getting at least one White sock?

#### lyner

• Guest
##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #5 on: 25/10/2008 20:55:06 »
In a totally random process, you can expect any result. There may be a bias towards one result so that there may not be an even split in probabilities. For the statistics to reveal this bias, it is necessary to have an enormous number of results / observations / measurements.
All statistics have a 'significance' associated with them which gives an indication of how reliable the figures are. In such a sparse set of data, there is very little significance in any result.

#### lyner

• Guest
##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #6 on: 25/10/2008 21:02:31 »
Quote
The probbility is 100% because they do.

The concept of 'probability' doesn't really apply to what has already happened. The definition of probability is 'the number of ways an event can occur divided by the total possible number of outcomes'. In one recorded outcome you could say that the probability is 100% but what were the possible outcomes?

Basically, statistics is not a subject for speculation. . . . . ?

#### The Naked Scientists Forum

##### Re: What is the probability of 5 presidents out of 43 being left handed?
« Reply #6 on: 25/10/2008 21:02:31 »