**GENEALOGY-DNA-L Archives**

From:"Lancaster-Boon" <>Subject:[DNA] Odds Are, It's Wrong - 5% of the timeDate:Sat, 20 Nov 2010 09:53:53 +0100Hi Steve

I guess that there is a legitimate point to be made, and it is connected to

the point Ken now made, that in our time there are now an enormous number of

people who have learnt how to manipulate numbers and formulas and get those

manipulations through peer review, but it is possible to be skilled in doing

this without being skilled in interpretation back into the real world.

Very often reports about tolerance intervals etc are almost meaningless

because they compare to a model of reality that is itself not certainly

correct. That is of course not how it is when we talk about rolling a dice

or flipping a coin, because the "models" of the probabilities on each roll

or flip are simple and well-known.

So, in summary, flipping a coin or rolling a dice, while useful for learning

the maths, is not so perfect for explaining the difficulties of

interpretation of the maths back into real world models.

I hope what I have written makes some level of sense! :D

Best Regards

Andrew

===========

From: Steven Bird <>

Subject: [DNA] Odds Are, It's Wrong - 5% of the time

Date: Fri, 19 Nov 2010 20:00:17 -0600

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In-Reply-To: <>

The cumulative odds of losing three times in a row, given a 19 out of 20

chance to win on each play, are exactly what I stated. .05*.05*.05=.000125

or .00205% The odds of each chance remain 19 out of 20, but cumulative odds

of winning ONE time increase. If I flip a fair coin, the chance of heads is

50/50. However, the chance of NO heads in ten tosses diminishes to 0.5^10,

or .000977.

As I indicated before, if you are unhappy with a 95% chance of being right,

then change the p value to 99.7% or 99.9999%. It is strictly up to the

statistician. There is nothing sacred about p=0.05

You might be right about the double or nothing bet however. ;-)

**This thread:**

- [DNA] Odds Are, It's Wrong by Wilcox Lisa <>
- Re: [DNA] Odds Are, It's Wrong by Al Aburto <>
- Re: [DNA] Odds Are, It's Wrong by "Ken Nordtvedt" <>
- Re: [DNA] Odds Are, It's Wrong by Al Aburto <>

- Re: [DNA] Odds Are, It's Wrong by "Alister John Marsh" <>

- Re: [DNA] Odds Are, It's Wrong by "Ken Nordtvedt" <>

- Re: [DNA] Odds Are, It's Wrong - 5% of the time by Steven Bird <>
- Re: [DNA] Odds Are, It's Wrong - 5% of the time by Steven Bird <>

- Re: [DNA] Odds Are, It's Wrong - 5% of the time by Gareth Henson <>
- Re: [DNA] Odds Are, It's Wrong - 5% of the time by "Ken Nordtvedt" <>
- Re: [DNA] Odds Are, It's Wrong - 5% of the time by Wilcox Lisa <>
- Re: [DNA] Odds Are, It's Wrong - 5% of the time by "Ken Nordtvedt" <>

- Re: [DNA] Odds Are, It's Wrong - 5% of the time by Wilcox Lisa <>

- Re: [DNA] Odds Are, It's Wrong - 5% of the time by "Ken Nordtvedt" <>

- Re: [DNA] Odds Are, It's Wrong - 5% of the time by James Heald <>

**[DNA] Odds Are, It's Wrong - 5% of the time by "Lancaster-Boon" <>**

- Re: [DNA] Odds Are, It's Wrong by Al Aburto <>