Public Health Emergency Preparedness
This resource was part of AHRQ's Public Health Emergency Preparedness program, which was discontinued on June 30, 2011, in a realignment of Federal efforts.
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Appendix A: Technical Notes
Data Sources
To develop the maps in the Atlas, we used
three national datasets to obtain information on
hospitals, nursing homes, and demographics in
each of the 50 States and the District of Columbia.
We underscore the fact that data representations
are cross-sectional snapshots for a given period
of time.
Hospitals
The locations of hospitals and data related to
total beds, admissions, and staffing were obtained
from the American Hospital Association (AHA)
2005 Annual Hospital Survey. The survey represents
both AHA member and nonmember hospitals and
gathers information on organizational structure,
facilities and services, utilization, finances, and
staffing. The average annual response rate is 83
percent; information for hospitals not responding
to the survey is estimated using data from previous
years.
Although the AHA Annual Hospital Survey
serves as the most comprehensive inventory
of hospitals, not all hospitals are included. An
institution is listed by the AHA as a hospital if it is
accredited as a hospital by the Joint Commission
on Accreditation of Healthcare Organizations
(JCAHO), is certified as a provider of acute services
under Title 18 of the Social Security Act, or is
licensed as a hospital by the appropriate State
agency (AHA, 2005). Only acute care general
hospitals are included in the Atlas. Long-term
care, specialty, rehabilitation, and psychiatric
hospitals were excluded. Counts of facilities, beds,
admissions (total and emergency department),
and full-time equivalent (FTE) registered nurses
were created by summing the totals for all facilities
located within a county.
Skilled Nursing Facilities/Nursing Facilities
The locations of nursing homes and data
related to beds and staffing were obtained from
the Centers for Medicare & Medicaid Services
(CMS) December 2004 Provider of Services file.
These data are collected by CMS through the
Online Survey Certification and Reporting (OSCAR)
data collection network, which contains the most
comprehensive source of facility-level information
on the operations, patient census, and regulatory
compliance of nursing facilities.
A nursing home
located within a hospital is included as a separate
nursing home facility. At times, the reader may
notice that hospitals and nursing home symbols are
located directly on top of one another on a map.
This indicates that these facilities are colocated.
Other types of post-acute care facilities, such as
long-term care hospitals, psychiatric facilities, and
inpatient rehabilitation facilities, were not included
in the Atlas. Counts of facilities, beds, and FTE
registered nurses were created by summing the
totals for all facilities located within a county.
Demographics
Population counts classified by age, sex, and
urban versus rural residence were obtained from
the Census 2000 Summary File 3, available on the
U.S. Census Bureau's Web site (http://www.census.gov).
These data were used to calculate the percentage
of the population aged 65 or older and the
percentage of the population living in an urban
area that were used to create the base maps in the
Atlas. Population pyramids were also developed to
show the age and sex distribution of the population
by summing population counts into 5-year age
groups by sex.
Geographic Boundaries
International, State, county, and census tract
boundaries, as well as roads and major water
bodies, were obtained from ESRI in Redlands,
California. To support its software, ESRI has
developed a wide range of datasets that define
basic geopolitical boundaries (often referred
to as base maps), transportation networks,
and other geographic features. Much of ESRI's
data are available online free of charge at http://www.geographynetwork.com.
The boundaries for the Health Resources and Services Administration
(HRSA) Bioterrorism Hospital Regions, Metropolitan
Medical Response System (MMRS), Emergency
Medical Services (EMS) Regions, Emergency
Management (EM) Regions, Hazardous Materials
(HAZMAT) Regions, and Trauma Coordination
Regions were developed using information
collected through telephone conversations with
State emergency planners and Internet searches.
Graphical Layout
Basic Map Style
Most of the maps in the Atlas are choroplethic
maps, in which geographic units (e.g., counties) are
shaded to represent different values of a variable.
When the data are continuous in nature (e.g.,
percentage or ratio), data values are grouped into
several ranges, or "classes." The legends on each
map page indicate the range of data values that
each color represents. These maps are useful when
data have been scaled or normalized in some way.
When data are nominal in nature, data values are
grouped into discrete categories, and a different
color is assigned to each category.
An important feature of maps is the ability to
represent multiple datasets. Each map synthesizes
information from different sources into a
comparative visual display. For example, many of
the maps in the Atlas integrate data from the AHA
(red cross symbols for the location of hospitals)
and the CMS (purple circle symbols for the location
of nursing homes). These symbols are graduated
(change size) proportional to the number of beds in
a facility (their bed size) in a given area. The legend
on each map page indicates the range of bed sizes
that each size symbol represents.
Titles, Legends, Captions
Most map titles list the geographic reference
(e.g., State name) and the theme of the map.
Legend captions provide a more detailed
explanation of the data displayed on the map.
The reader should begin by reading the title to
understand the general topic of the map, followed
by the legend for explicit details about the data,
and finally closely examine the map.
Classes
There are many different methods for deciding
class breaks, or data ranges, for choroplethic maps.
In the Atlas, we enable comparison between maps
by using the same class breaks across maps. For
example, the percentage of the population living in
an urban area has the same class breaks across all
of the 51 State maps as well as the case study maps
that use this variable.
The class breaks used for the maps were
developed using the "natural break" method.
The natural breaks classing method identifies
logical breaks, or groupings, that naturally exist
in the data. These logical breaks are identified
by making a bar graph showing the frequency
distribution of the data (e.g., a histogram). For
example, the frequency distribution of the data on
the percentage of the population living in an urban
area showed a gap in the data values between 8
and 10 percent. There were many areas with 8 or 10 percent of the population living in an urban area
but fewer areas with 9 percent of the population
living in an urban area. A natural break in the data
occurs between 8 and 10 percent, so 9 percent
becomes the end of one class break and the
beginning of another.
The natural breaks for the six case study States
were visually examined and combined to create a
consistent class system for all of the maps in the
Atlas. Both the demographic data and the facilities
data were classed using this same method.
Color
Color assists the reader in understanding the
data and should reflect the subject matter of
the map as well as the values of the data. The
appropriate use of color is important because it
reduces the chances of seeing patterns that do not
exist or missing patterns that do.
The Atlas uses color schemes developed
by Cynthia Brewer (1994). The color schemes
were developed to be accessible to individuals
who are color-blind and can be photocopied in
black and white without loosing contrast. These
color schemes can be accessed through a Web-based
application called ColorBrewer at http://www.colorbrewer.org.
On many of the maps, colors are arranged
from dark to light, with dark colors representing
high values and light colors representing low
values. For example, dark blue corresponds to a
high percentage of an elderly population living
in an area. On the regional maps (i.e., HAZMAT,
Trauma, EMS, and EM), color schemes were used
to delineate the different regions. These colors do
not correspond to a value; rather, they are chosen
to make identifying each region as easy as possible.
For example, in North Carolina, EMS Regions 1 and
2 are adjacent to each other, so contrasting colors
of purple were chosen to represent each area.
Finally, pre-press files were prepared for fourcolor
separation according to the U.S. Government
Printing Office (GPO) guidelines for best practices
for submitting electronic design and pre-press files.
Hatching
Occasionally, areas on a map are hatched, or
symbolized by diagonal lines. The addition of
hatched lines is used to convey an additional piece
of information, such as the presence of an MMRS,
without masking other data on the map, such as color.
Software
The maps in the Atlas were created using
ArcView 9 [for Windows®, 2004] geographic
information and mapping software from ESRI. Data
on the total beds and location of hospitals and
nursing homes and demographic characteristics
of the population were loaded into the ArcView
software and used in conjunction with ESRI's
geographic data (i.e., geopolitical boundaries and
transportation networks) to develop the maps in
the Atlas. Publication of the Atlas was prepared
using the following software: Adobe® InDesign
CS 2, Adobe® Illustrator CS 2, and Adobe®
PhotoShop CS 2.
References
Brewer CA. Color use guidelines for mapping and
visualization. In: MacEachren AM, Taylor DRF, eds.
Visualization in Modern Cartography. Oxford,
England: Pergamon Press; 1994:123-47.
American Hospital Association. AHA Guide to the
Health Care Field. Washington, DC: American
Hospital Association; 2005.
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