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Hi, Cliff
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(a)camsys.com
www.camsys.com
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Today's Topics:
1. How to Combine Median Values for Mutliple Areas (Cook, Cliff)
2. RE: How to Combine Median Values for Mutliple Areas (Eric Kramer)
----------------------------------------------------------------------
Message: 1
Date: Mon, 3 Jan 2011 13:24:06 -0500
From: "Cook, Cliff" <ccook(a)cambridgema.gov>
Subject: [CTPP] How to Combine Median Values for Mutliple Areas
To: "ctpp-news(a)chrispy.net" <ctpp-news(a)chrispy.net>
Message-ID: <600EBD94B0166D4BADC1083702EC47C4026F6C522B(a)Mordac.City>
Content-Type: text/plain; charset="us-ascii"
I am looking for guidance on how to combine median income values for
several census tracts into a single value and associated margin of error.
I recall seeing something about this topic in an ACS document but cannot
locate the information at this time. Any help would be appreciated.
Cliff Cook
-----------------------------------------------------------------------------
Clifford Cook
Planning Information Manager
Cambridge Community Development Dept.
344 Broadway
Cambridge, MA. 02139
617/349-4656 FAX 617/349-4669 TTY 617/349-4621
email => ccook(a)cambridgema.gov
web site => <http://www.cambridgema.gov/~CDD/>
