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#1




1) the negative paraxes...
...from the topic ''Letter to a friend ''
... the negative parallaxes are a big mistery , as i told many times ... almost nobody want to speak about it , and almost all don't know its existence ... Eistein and de Sitter could not imagine a similar thing ... not only , untill the years 2000 nobody had suspected that existence ... so difficult to understand ! but exactly the half of not near bodies ( stars , galaxies , quasars..) have a negative parallaxes .. and you must make alone all the mental paths around its .. no books , no profs ,no magicians ...: i can only say my opinions ..and discuss with you that opinions , trying togheter a reasonable street where nobody walked .. ( i think that the negative parallaxes ' solution can influence directly the dark matter and the age of universe ) .. main asks and next program : 1) what is a parallax and a negative parallax? 2) how a negative parallax can enter in our science? 
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#2




1) the negative paraxes...

#3




1) the negative paraxes...
Dne 11/12/2016 v 17:57 Mike Dworetsky napsal(a):
Your suspicion is correct. If you have a list of parallaxes of very distant objects, so that their parallaxes are on average much smaller than your limit of detection, then the errors of parallax are distributed normally, with a bellshaped curve plotting the likely distribution of values around a mean of nearly zero. Hence we expect there to be approximately half of those published parallaxes with values less than zero and half with values more. The question remains, why the data with parallax value within the measurement error is not replaced by an appropriate note, instead of publication of noise.  Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject. 
#4




1) the negative paraxes...
Poutnik wrote:
Dne 11/12/2016 v 17:57 Mike Dworetsky napsal(a): Your suspicion is correct. If you have a list of parallaxes of very distant objects, so that their parallaxes are on average much smaller than your limit of detection, then the errors of parallax are distributed normally, with a bellshaped curve plotting the likely distribution of values around a mean of nearly zero. Hence we expect there to be approximately half of those published parallaxes with values less than zero and half with values more. The question remains, why the data with parallax value within the measurement error is not replaced by an appropriate note, instead of publication of noise. For exactly the reason I stated in the part of my reply that you snipped: Negative values are unphysical, but form the part of the statistical distribution of values that happen to lie below zero when the mean is close to zero. Imagine that someone plotted a graph of, say, a spectrum (with low S/N), and wherever the plotted flux was below zero, they simply truncated it. Would you be happy with that? I wouldn't.  Mike Dworetsky (Remove pants sp*mbl*ck to reply) 
#5




1) the negative paraxes...
Dne 11/12/2016 v 22:50 Mike Dworetsky napsal(a):
Poutnik wrote: The question remains, why the data with parallax value within the measurement error is not replaced by an appropriate note, instead of publication of noise. For exactly the reason I stated in the part of my reply that you snipped: Negative values are unphysical, but form the part of the statistical distribution of values that happen to lie below zero when the mean is close to zero. Positive and negative noise values are equally unphysical. Imagine that someone plotted a graph of, say, a spectrum (with low S/N), and wherever the plotted flux was below zero, they simply truncated it. Would you be happy with that? I wouldn't. IMHO He should truncated all measurements with zero belonging to CI of the measurement (mean) value, as with statistically insignificant difference to zero.  Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject. 
#6




1) the negative paraxes...
On 12/12/2016 06:42, Poutnik wrote:
Dne 11/12/2016 v 22:50 Mike Dworetsky napsal(a): Poutnik wrote: The question remains, why the data with parallax value within the measurement error is not replaced by an appropriate note, instead of publication of noise. For exactly the reason I stated in the part of my reply that you snipped: Negative values are unphysical, but form the part of the statistical distribution of values that happen to lie below zero when the mean is close to zero. Positive and negative noise values are equally unphysical. But you only know for certain that the negative values are unphysical the positive ones could be real to within some measurement error. Later more refined experiments may be able to narrow down the error bars. BTW The speed of light in vacuum with error bars displayed makes salutary reading for anyone over confident in good experimental method. Essentially one famous experimenter applied a partial vacuum correction in the wrong direction for a new method and everyone copied him until an even more exquisitely sensitive technique gave a different answer. So for a couple of decades the speed of light was very precisely wrong due to unrecognised systematic errors. The graph was in an introductory relativity book but I forget which one  anyone recognise it from this? Imagine that someone plotted a graph of, say, a spectrum (with low S/N), and wherever the plotted flux was below zero, they simply truncated it. Would you be happy with that? I wouldn't. IMHO He should truncated all measurements with zero belonging to CI of the measurement (mean) value, as with statistically insignificant difference to zero. No. Provided that it is stated somewhere what the limits of detection for the method actually is then the value determined even if it is negative is more useful to later researchers than a "below LOD" flag.  Regards, Martin Brown 
#7




1) the negative paraxes...
Dne 13/12/2016 v 09:44 Martin Brown napsal(a):
On 12/12/2016 06:42, Poutnik wrote: For exactly the reason I stated in the part of my reply that you snipped: Negative values are unphysical, but form the part of the statistical distribution of values that happen to lie below zero when the mean is close to zero. Positive and negative noise values are equally unphysical. But you only know for certain that the negative values are unphysical the positive ones could be real to within some measurement error. Later more refined experiments may be able to narrow down the error bars. Later experiment can. But I speak in context of this one. These small values are not statistically justified, as there is high probability it is just a noice. Imagine that someone plotted a graph of, say, a spectrum (with low S/N), and wherever the plotted flux was below zero, they simply truncated it. Would you be happy with that? I wouldn't. IMHO He should truncated all measurements with zero belonging to CI of the measurement (mean) value, as with statistically insignificant difference to zero. No. Provided that it is stated somewhere what the limits of detection for the method actually is then the value determined even if it is negative is more useful to later researchers than a "below LOD" flag. One thing is raw data, other thing is published processed data. The limits should be available to a team of original data. Such a limit can be estimated from the fluctuation around zero, for stars where expected value is low enough.  Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject. 
#8




1) the negative paraxes...
Il giorno mercoledÃ¬ 14 dicembre 2016 08:44:15 UTC+1, Poutnik ha scritto:
Dne 13/12/2016 v 09:44 Martin Brown napsal(a): On 12/12/2016 06:42, Poutnik wrote: For exactly the reason I stated in the part of my reply that you snipped: Negative values are unphysical, but form the part of the statistical distribution of values that happen to lie below zero when the mean is close to zero. Positive and negative noise values are equally unphysical. But you only know for certain that the negative values are unphysical the positive ones could be real to within some measurement error. Later more refined experiments may be able to narrow down the error bars. Later experiment can. But I speak in context of this one. These small values are not statistically justified, as there is high probability it is just a noice. Imagine that someone plotted a graph of, say, a spectrum (with low S/N), and wherever the plotted flux was below zero, they simply truncated it. 
#9




1) the negative paraxes...


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