Limitation of ratio analysis Video
22.27 Limitations of Ratio Analysis limitation of ratio analysis.Calculate Density Ratio uses two input point datasets to calculate a spatial relative risk surface.
The numerator in the ratio represents cases, such as anallysis of crimes or number of patients, and the denominator represents the control, such as the total population. Calculate Density Ratio uses the same calculations to create density surfaces as Calculate Density. The outputs of Calculate Density and Calculate Density Ratio may appear similar; however, the output of Calculate Density Ratio is normalized, meaning it displays a proportional value, whereas the output of Calculate Density is not. Use a density ratio when the phenomenon being analyzed requires a control, such as total population.
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The individual density surfaces are calculated using Kernel density before the ratio is calculated. An epidemiologist is studying the occurrences of a disease to determine if high occurrences in certain areas could be linked to environmental factors. The density ratio is calculated using the disease occurrences as the numerator and the total population as the denominator. The result surface shows the density of disease occurrence normalized by population density, which makes it possible to determine where the disease occurrences are higher than expected. You can run Calculate Density Limitation of ratio analysis on maps with point layers.
Two separate datasets are required as input. Complete the following steps to run the Calculate Density Ratio analysis capability:.
A card is active when the toolbar and Action button appear. The Choose point layers parameter is used to select datasets to calculate densities for the numerator and denominator. Only point features are available as inputs.]
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