**GENEALOGY-DNA-L Archives**

From:Steven Bird <>Subject:[DNA] P value (was chances are, it's wrong)Date:Sat, 20 Nov 2010 12:37:57 -0600References:<F9C440A2-FC59-4A9E-AAAC-85DEE9D2FAB0@GMAIL.COM>, ,<COL115-W50D879F102DC3996D9D454A03A0@phx.gbl>, ,<4CE7A3C0.7050702@ucl.ac.uk>, ,<COL115-W1464B78AF0292D6AEFA183A03B0@phx.gbl>,<COL115-W5950BB2C58A31B4806036EA03B0@phx.gbl>,<4CE8088B.3020500@ucl.ac.uk>,<COL115-W45724B549DCDA5DD2EC4A0A03B0@phx.gbl>In-Reply-To:<COL115-W45724B549DCDA5DD2EC4A0A03B0@phx.gbl>James wrote:

> P-value has a very precise meaning in Frequentist statistics.

> It is "the probability of obtaining a test statistic at least as extreme

> as the one that was actually observed, assuming that the null hypothesis

> is true".

> http://en.wikipedia.org/wiki/P-value

I reply:

It is also defined as the probability of committing a Type I error (rejecting the null when it is in fact true or a false positive) when using a statistic such as student's T test. When p=0.05, it means that the statistician have a 1 in 20 chance of being wrong (falsely rejecting the null) when the null is in fact true. To me, that is identical in meaning with the statement that he or she also has a 19 out of 20 chance of being right. How is it different?

**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 <>