From: Alexander Conley (AJConley@lbl.gov)
Date: Sun Nov 07 2004 - 01:06:32 PST
There was definitely something wrong with the values given in the paper
for the mean slopes and the error in that mean.
In any case, the new values are:
Low-z: beta = 1.9854 +- 0.0299
High-z: beta = 1.9654 +- 0.1130
There are 47 low-z and 5 high-z, so you expect a sqrt(10) = 3
improvement,
but for some reason there is a factor of 4. With only 5 SNe involved,
this probably
doesn't mean much -- I suppose one could estimate the error in the rms
or something.
The addition of a few extra low-z SNe has dragged the mean slope up
slightly for
the low z sample (by maybe 0.02).
I thought for a while about using the weighted mean for this, but I
don't
think it's valid. The weighted mean seems to require that all of the
measurements
are of the same quantity, and since I believe that there is some
intrinsic dispersion
in the slopes, this doesn't apply. The raw mean, on the other hand, has
it's own life. In any case, using a weighted mean decreases the error
in the low-z
sample by about a factor of two, but doesn't really do anything for the
high-z sample.
They are consistent -- but the high-z error is pretty big.
Alex
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