The 'Science' article is attached, along with a letter from one of the
authors.
It claims " that the authors of the (Lancet) report have destroyed the
information on where and how they sampled!"
JOHN BIBBY
> -----Original Message-----
> From: Spagat M [mailto:[log in to unmask]]
> Sent: 20 October 2006 16:45
> To: John Bibby; [log in to unmask]; [log in to unmask]
> Subject: RE: Iraq again
>
>
> Dear Mr. Bibby,
>
> Thank you for your interest. Very good question. I'll try to dash off
> a reply with very little time at my disposal. Please excuse some
> roughness.
>
> First let's distinguish two concepts of distance.
>
> 1. How far you have to walk to get somewhere ("normal distance").
> 2. How many times you have to change streets to get somewhere ("network
> distance")
>
> We'll say crossroads to a main road are at network distance 1,
> crossroads to crossroads at distance 2, etc. It's true that some
> houses at network distance 2 will be closer to the main road in terms of
> normal distance than some houses at network distance 1. But the average
> normal distance of houses at network distance 1 will always be lower
> than the average distance of the households at network distance 2. Why?
> Start from a cross road to a cross road to a main street. To travel to
> the main street you must first go to a cross road to the main street.
> Only then can proceed to the main street.
>
> This is all just to say that network distance and normal distance work
> similarly. Both concepts reinforce the main street bias point. The
> Lancet team sampled households that were closer than average to the main
> streets both in terms of normal distance and in terms of network
> distance. But increasing either network distance or normal distance
> will decrease the risk of violence.
>
> Let's put it a different way. They may have sampled some households
> fairly far away from main streets. But any time they did this there
> would have been other neighborhoods still farther away, both in the
> usual and the network senses, that could not have been sampled.
>
> You also wonder if it's possible to check how often they sampled far
> from main streets. Sadly the answer would appear to be know. I'm
> guessing that you saw only our press release and not the related article
> in Science (attached). This article reveals that the authors of the
> report have destroyed the information on where and how they sampled!
> How about that?
>
> I could make a few big points.
>
> In correspondence connected with the Science article one of the authors
> of the Lancet paper defined main roads as "major roads and commercial
> avenues". This would pretty much seem to rule out sampling from
> anyplace rural or without well-paved roads.
>
> Finally, they say that once the street was chosen they numbered the all
> the houses and selected one at random. They didn't have a list of
> households to begin with or they wouldn't be doing this craziness in the
> first place. So they would have had to build one with very limited
> time. (Remember that they conducted 40 interviews per day) So even in
> urban areas it seems unlikely that they would strayed very far from main
> roads.
>
> How this was clear.
>
> Mike Spagat
>
>
>
>
>
> Professor Michael Spagat
> Department of Economics
> Royal Holloway College
> University of London
> Egham
> Surrey
> TW20 0EX
> United Kingdom
> +44 1784 414001 (W)
> +44 1784 439534 (F)
> [log in to unmask]
> http://personal.rhul.ac.uk/uhte/014
>
>
>
> -----Original Message-----
> From: John Bibby [mailto:[log in to unmask]]
> Sent: 20 October 2006 14:12
> To: [log in to unmask]; [log in to unmask];
> [log in to unmask]
> Subject: Iraq again
>
>
> Dear Gentle-people
>
> Interesetd in your report on Iraq - do you have any comments on the
> following?
>
> ==========
> The BBC mentioned a study yesterday that refuted the 600,000 figure on
> the grounds that "houses near main roads were over-represented" (my
> paraphrase).
>
> >From the Lancet article it does appear that households on SHORT street
> near main roads will have been over-represented. (However, households on
> main roads appear not to have been sampled at all.
>
> If "distance from main road" was collected, as it easily could have
> been, it would be possible to attempt some control for this factor.
>
> Has anybody been in touch with the Johns Hopkins people about our
> discussion? (I bet they are fed up with it by now!)
>
> ========
> I was concerned by Triesman's explanation of why the UK government does
> not interest itself with the accuracy of such figures. (see Ted
> Harding's earlier email.)
>
> JOHN BIBBY
>
> ========== From NZ!: http://www.scoop.co.nz/stories/WO0610/S00436.htm
>
> Lancet Iraq Study Flawed: Death Toll Too High
> Friday, 20 October 2006, 10:36 am
> Press Release:
> Lancet Study Fundamentally Flawed: Death Toll Too High
> October 19, 2006 - 1 page -
> For immediate release:
>
> Researchers at Oxford University and Royal Holloway, University of
> London have found serious flaws in the survey of Iraqi deaths published
> last week in the Lancet.
>
> Sean Gourley and Professor Neil Johnson of the physics department at
> Oxford University and Professor Michael Spagat of the economics
> department of Royal Holloway, University of London contend that the
> study's methodology is fundamentally flawed and will result in an
> over-estimation of the death toll in Iraq.
>
> -> The study suffers from "main street bias" by only surveying houses
> -> that
> are located on cross streets next to main roads or on the main road
> itself. However many Iraqi households do not satisfy this strict
> criterion and had no chance of being surveyed.
>
> -> Main street bias inflates casualty estimates since conflict events
> -> such
> as car bombs, drive-by shootings artillery strikes on insurgent
> positions, and market place explosions gravitate toward the same
> neighborhood types that the researchers surveyed.
>
> -> This obvious selection bias would not matter if you were conducting a
> simple survey on immunisation rates for which the methodology was
> designed.
>
> -> In short, the closer you are to a main road, the more likely you are
> -> to
> die in violent activity. So if researchers only count people living
> close to a main road then it comes as no surprise they will over count
> the dead.
>
> During email discussions between the Oxford-Royal Holloway team and the
> Johns Hopkins team conducted through a reporter for Science, for an
> article to be published October 20, it became clear that the authors of
> the study had not implemented a clear, well-defined and justifiable
> methodology. The Oxford-Royal Holloway team therefore believes that the
> scientific community should now re-analyze this study in depth.
>
>
> The team can be reached for comment at;
>
> Gourley: s.gourley1 @ physics.ox.ac.uk mobile:+44 (0) 7733113558
> [log in to unmask] [log in to unmask]
> [log in to unmask]
>
> --
Thank you and Best Regards
JOHN BIBBY aa42/MatheMagic
1 Straylands Grove, York YO31 1EB (01904-330 334) NB: New phone 2005
NB: Visit *** www.tarquinbooks.com *** for a special gift - put 'aa42'
after your name when ordering.
All statements are on behalf of aa42.com Limited, a company wholly owned by
John Bibby and Shirley Bibby. See www.aa42.com/mathemagic and
www.mathemagic.org
> -----Original Message-----
> From: email list for Radical Statistics
> [mailto:[log in to unmask]]On Behalf Of John Bibby
> Sent: 20 October 2006 14:11
> To: [log in to unmask]
> Subject: Iraq again
>
>
> The BBC mentioned a study yesterday that refuted the 600,000 figure on the
> grounds that "houses near main roads were over-represented" (my
> paraphrase).
>
> >From the Lancet article it does appear that households on SHORT
> street near
> main roads will have been over-represented. (However, households on main
> roads appear not to have been sampled at all.
>
> If "distance from main road" was collected, as it easily could
> have been, it
> would be possible to attempt some control for this factor.
>
> Has anybody been in touch with the Johns Hopkins people about our
> discussion? (I bet they are fed up with it by now!)
>
> ========
> I was concerned by Triesman's explanation of why the UK
> government does not
> interest itself with the accuracy of such figures. (see Ted Harding's
> earlier email.)
>
> JOHN BIBBY
>
> ========== From NZ!: http://www.scoop.co.nz/stories/WO0610/S00436.htm
>
> Lancet Iraq Study Flawed: Death Toll Too High
> Friday, 20 October 2006, 10:36 am
> Press Release:
> Lancet Study Fundamentally Flawed: Death Toll Too High
> October 19, 2006 – 1 page –
> For immediate release:
>
> Researchers at Oxford University and Royal Holloway, University of London
> have found serious flaws in the survey of Iraqi deaths published last week
> in the Lancet.
>
> Sean Gourley and Professor Neil Johnson of the physics department
> at Oxford
> University and Professor Michael Spagat of the economics
> department of Royal
> Holloway, University of London contend that the study’s methodology is
> fundamentally flawed and will result in an over-estimation of the
> death toll
> in Iraq.
>
> -> The study suffers from "main street bias" by only surveying houses that
> are located on cross streets next to main roads or on the main
> road itself.
> However many Iraqi households do not satisfy this strict criterion and had
> no chance of being surveyed.
>
> -> Main street bias inflates casualty estimates since conflict events such
> as car bombs, drive-by shootings artillery strikes on insurgent positions,
> and market place explosions gravitate toward the same neighborhood types
> that the researchers surveyed.
>
> -> This obvious selection bias would not matter if you were conducting a
> simple survey on immunisation rates for which the methodology was
> designed.
>
> -> In short, the closer you are to a main road, the more likely you are to
> die in violent activity. So if researchers only count people
> living close to
> a main road then it comes as no surprise they will over count the dead.
>
> During email discussions between the Oxford-Royal Holloway team and the
> Johns Hopkins team conducted through a reporter for Science, for
> an article
> to be published October 20, it became clear that the authors of the study
> had not implemented a clear, well-defined and justifiable methodology. The
> Oxford-Royal Holloway team therefore believes that the scientific
> community
> should now re-analyze this study in depth.
>
>
> The team can be reached for comment at;
>
> Gourley: s.gourley1 @ physics.ox.ac.uk mobile:+44 (0) 7733113558
> Johnson: n.johnson @ physics.ox.ac.uk
> Spagat: M.Spagat @ rhul.ac.uk
>
--
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