Technical Guide
Overview
The following pages offer detailed descriptions of the methodology used to identify priority
NSAs for each variable:
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Data Considerations
Most variables in this report were generated using locally-based data sources. Descriptions of
considerations related these data sources are included for each variable. Additional general data
considerations used in developing the methodology include:
•
Zip code-based data
: In instances where data was collected and analyzed at the zip code
scale, the results for each zip code were assigned to the NSAs whose centroids fell in the
zip code boundary.
One NSA falls inside the zip code 23702, only part of which lies inside of City of
Chesapeake boundaries. The U.S. Census classifies this portion of 23702 as part of the
23323 Zip Code Tabulation Area (a level of analysis similar to census tracts and block
groups). Further, most Chesapeake resources did not included data for this zip code. For
all analyses requiring zip code-level analysis, the NSA falling inside 23702 was assigned
to 23323.
•
Census and ACS-based data
: Where possible, the most recent Census or American
Community Survey-based data was used. Data sources are noted in the descriptions.
•
Margins of error:
Matching address points to NSAs in GIS resulted in incomplete results,
as some addresses were located outside of the city boundaries. If the address matching
results produced less than a five percent margin of error, the results were included in the
analysis.
•
Z scores:
A Z score indicates how many standard deviations above or below the mean the
original data is. Z scores highlight in-need NSAs to prioritize investments. In some
instances, a reverse Z score was calculated to make high Z scores reflect high priority (in-
need) NSAs.
November 2014
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