Nanda and I just briefly discussed your
question on the median value calculation. We come up with two options:
1. The median income should be
available for each Census Tract. You can take total households for
each census tract as weights, using the weighted average for the median
household income across these Census Tracts. Then MOEs can be calculated
using the formula of weighted mean.
2. You can combine the distribution
of household incomes for each census tract and derive a single distribution
for aggregated Census tracts. Then you can come up with a median
value.
Using these methods, you will need to
interpolate MOEs for the upper bound and the lower bound.
Both these methods will not give you
the real median values - they are only ballpark figures. But you
can definitely try both and see which one is better.
Liang Long
Cambridge Systematics, Inc.
4800 Hampden Lane
Suite 800
Bethesda, MD 20814
tel 301 347 9141
fax 301 347 0101
FHWA 202-366-6971
e-mail llong@camsys.com
www.camsys.com
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01/03/2011 02:39 PM
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