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Archiver > GENEALOGY-DNA > 2011-02 > 1297265538


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] variance quiz game
Date: Wed, 9 Feb 2011 08:32:18 -0700
References: <002701cbc7a9$8c29ef30$c2482dae@Ken1><000001cbc842$3e876b10$bb964130$@com><000c01cbc86c$2641c9e0$c2482dae@Ken1>


Oops, I forgot factor 2 in my denominator. It is corrected below
----- Original Message -----
From: "Ken Nordtvedt" <>
To: <>
Sent: Wednesday, February 09, 2011 8:15 AM
Subject: Re: [DNA] variance quiz game


>
>
> ----- Original Message -----
> From: "Sandy Paterson" <>
>
>> I've forgotten the general form. Is it (for 67 markers)
>>
>> G = [ Var(1) + Var(2) + ....Var(67) ] / [ 67 x 2 x m ]
>>
>> where m is the mean of the mutation rates?
>>
>> Sandy
>
>
> That's the text book formula, although "67 times mean m" should probably
> be
> stated as "M = Sum of marker rates". Although the two quantities are
> obviously identical I have always thought it a "crime" what the former did
> to most all newcomers in sending them down the wrong conceptual path.
>
> When the TMRCAs get to be sufficiently old so that some of the m(i)G
> values
> are not much less than 1, the estimator for N markers should read,
> however:
>
> G = [ Var(1) w(1) + ....... Var(N) w(N) ]
> divided by 2 [ m(1) w(1) + ....... m(N) w(N) ]
>
> with weight factors w(i) = 1 / [ 1 + 4 m(i) G ]
>
> This gives tighter sigma to the G distribution.
>
>
>
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