Moran's I
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Indications/Recommendations for use: Nearby areas tend to have similar rates when their populations and exposures are alike. When
rates in connected (nearby) areas are similar Moran's I will be large and positive. When rates in
connected areas are dissimilar Moran's I will be negative (more).
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Description: A test for spatial autocorrelation in disease rates. Moran's I is a weighted correlation coefficient used to detect departures from spatial randomness. Departures from randomness indicate spatial patterns such as clusters. Other kinds of pattern including geographic trend. Positive spatial autocorrelation generally indicates that nearby area have similar disease rates, indicating spatial clustering.
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Test statistic: Moran's I is a weighted product-moment correlation coefficient, where the weights
reflect geographic proximity. Values of I larger than 0 indicate positive spatial autocorrelation; values
smaller than 0 indicate negative spatial autocorrelation (definitions here).
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Null Hypothesis:
Disease rates are spatially independent.
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Alternative Hypothesis:
Disease rates are not spatially independent.
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GeoMed Inputs:
A Moran data file containing disease rates and a link file assigning connection
weights to locality pairs. Moran's I requires a Moran data file, a link file and the number of runs.
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GeoMed Outputs:
P-values
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Example Analysis
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Reference:
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Free software: PPA
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