The old saying about figures don't lie but liars can figure is exemplified
by your message beautifully. My professor in Statistics gave a good example
of false conclusions  -  he demonstrated from available data that there was
a 100% correlation between the increase of salaries of teachers in New York
State and the increase in sales of liquor over a period of a few years.
Conclusion ?  One possible - if you want to increase sales of liquor then
give the teachers a raise.
Bob Anibal
-----Original Message-----
From: Baldwin Robertson <[log in to unmask]>
To: Multiple recipients of list PARKINSN <[log in to unmask]>
Date: Friday, October 24, 1997 2:55 AM
Subject: Re: Response to PD Survey


>Mary,
>
>I responded to your survey as soon as I read it because it took me only a
>few minutes.  I did it, however, even though surveys of this kind are
>usually not reliable.  It is not that the questions you asked were
>deficient in any way, and I believe you would be objective in evaluating
>the answers.
>
>It is because retrospective studies are usually not a reliable way to
>establish correlations.  I say usually because if everyone on the list
>answered and gave the same answer, you would indeed have uncovered
>something of value.  But, results seldom turn out that way.  Usually the
>correlations one might observe in retrospective studies have no validity
>and are useful only as a suggestion of one thing to look for in a more
>reliable subsequent study.
>
>This point was made an article by William Feller in the throwaway
>periodical 'Scientific Research' many years ago.  I remember it well
>because it impressed me so much.  Feller is the author of the book for a
>course on probability that I took.  He was the first to present the subject
>in the now accepted way.  The book went through a number of printings.  He
>is well respected.
>
>His article in 'Scientific Research' was short and to the point.  He
>probably chose that magazine because he wanted as many people as possible
>to get the message, which no doubt is widely known by probability theorists
>and mathematical statisticians, but seems frequently to be ignored by
>epidemiologists.
>
>Feller said that if you consider 100 uncorrelated random variables
>generated by a computer and calculated the correlations between all pairs
>of them, you would find at least one pair with a convincingly large
>numerical correlation.  I do not recall the exact number, but I think it is
>something like 25 per cent or more, maybe even 50 per cent.  Statisticians
>would say that value of the numerical correlation is  'statistically
>significant.'  There are also a surprisingly large number  of pairs for
>which the calculated correlations are large enough that someone who didn't
>know the source of the data might say that there is convincing evidence of
>a correlation.   Again I do not recall the exact numbers, but I think they
>are in the 5 percent to 10 percent range.  All this for random numbers with
>absolutely no real (i.e. causal) correlation.
>
>I am not an expert in statistics, and so I do not have definitive
>information to give you about this.  I certainly am not skilled in
>designing a careful study.  But I think Feller's point leads one to be
>cautious about the interpretation of retrospective studies.
>
>Baldwin, 63/4
>8x25/100 carbi/levo-dopa,  5 mg Eldepryl per day
>[log in to unmask]
>
>
>----------
>From:  Mary Sheehan
>Sent:  Thursday, October 23, 1997 11:06 PM
>To:  Multiple recipients of list PARKINSN
>Subject:  Response to PD Survey
>
>My PD started 11 years ago with a frozen shoulder.  Bradykinesia and
>micrographia followed, but the doctors attributed my symptoms to the
>effects
>of the frozen shoulder.  It wasn't until 21 months ago that I was diagnosed
>with PD. After 11 years with PD, I am still in stage 1. I take only 5mg of
>Eldepryl daily and have recently started to take Mirapex.
>
>I am telling you this so you will understand my motivation for doing the
>survey.  I have been amazed at the different rates at which PD progresses,
> the different symptoms in each person and the different ways that each
>person is medicated.  I came up with a premise that the progression and
>symptoms of PD must relate to either personal lifestyle or to how PD
>presents
>in an individual .... or possibly to a combination of both.  I had hoped to
>use the resources of this list to find a pattern that made the progression
>of
>PD more predictable.  I have done some successful research in the past,
>although not in the medical field, and felt there were clues out there
>waiting to be uncovered.
>
>Unfortunately, with only 18 responses, it was impossible to draw any
>conclusions.  I had hoped for 100 responses, or more, out of the 1500
>people
>on the list.  What really upset me was the responses i received as to why
>people didn't respond.
>" I'm too busy to reply".  The whole survey couldn't have taken more than 5
>minutes to fill out. Most questions required only one-word answers.
>"I'm tired of all the surveys on this list."  In the year and a half I've
>been on this list I recall only two persons doing a survey.  I answer
>surveys
>in the small hope that maybe something will come out of it that will help.
>"The PD organizations can"t get together".  So let them do their research
>separately.  I have great respect for the researchers at the Parkinson's
>Institute and for my neuro who also does research and whom I thought would
>be
>interested in what we had to say.
>
>I'm sorry to be so wordy.  I put in several hours of work on the survey and
>was annoyed to find my efforts denigrated.  I'm probably only having a bad
>day, but I'm disappointed because I honestly thought we might put our heads
>together and discover something.  I will shut up now and in the future will
>avoid initiating surveys .  Thanks for letting me vent.
>
>Mary