chapter-2 - Characteristics of Geographic Data: CONCEPTS...

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Characteristics of Geographic Data: CONCEPTS PRIMARY DATA SOURCE : Data acquired directly from the source. The investigator has control over the data-gathering procedure. SECONDARY (ARCHIVAL) DATA SOURCE : Data acquired by an organisation or agency. Can be tremendous variation in collection methods and data quality. EXPLICITLY SPATIAL : Analyses in which spatial relationships (e.g., location or spatial arrangement) are directly considered. IMPLICITLY SPATIAL : An analyses in which spatial relationships are not directly considered. TYPES OF DATA SOURCES TYPES OF GEOGRAPHIC ANALYSES
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Characteristics of Geographic Data: CONCEPTS II INDIVIDUAL LEVEL : Analysis is at the level of the “fundamental unit” of individual observations. AGGREGATE LEVEL : Analyses at a higher level of organization than individual organizations. ECOLOGICAL FALLACY : An attempt at making inferences at a lower level of organisation than the level at which analyses were conducted. LEVEL OF ANALYSIS MODIFIABLE AREAL UNIT PROBLEM (MAUP) :The difficulty in determining the appropriate level of organisation for making inference.
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The ecological fallacy is a widely recognized error in the interpretation of statistical data, whereby inferences about the nature of individuals are based solely upon aggregate statistics collected for the group to which those individuals belong. This fallacy assumes that all members of a group exhibit characteristics of the group at large. Stereotypes are one form of ecological fallacy. In statistical terminology the equivalent term used is biased sampling and is avoided by using methods such as stratified sampling . Example. Imagine two communities, Chiptown and Pittsville . Within each community there is a divide between the rich and poor , the rich living in gated communities on the hills and the poor living adjacent to the industrial districts that pump carcinogens into their backyards. In both communities , the poor people have a cancer incidence that is many times that of the wealthy people. In Chiptown, where the dominant industry is high-tech computer manufacturing, the overall salaries are higher for both rich and poor people, but the carcinogens spewed into the environment are particularly nasty, giving cancer to nearly all those exposed (almost entirely poor people). Prof. Newbie comes along and decides to examine the risk factors for cancer. He looks up the cancer rates and median incomes of these two towns on the CDC and U.S. Census webpages. He finds, to everyone's surprise, that the cancer incidence is higher in the wealthier community, Chiptown. He concludes that higher income is a risk factor for cancer. In fact, we know that exactly the opposite is true: In the wealthier community of Chiptown, being poor is especially dangerous to one's health.
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If relations between variables change with the selection of different areal units, the reliability of results is called into question.
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This note was uploaded on 01/18/2011 for the course GEOG 339 taught by Professor Staff during the Fall '10 term at University of Calgary.

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chapter-2 - Characteristics of Geographic Data: CONCEPTS...

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