Table 2

Power of selected statistics for detecting data with local and global cluster types.

Global clustering methods

Local cluster detection methods



Tango_PDM

Tango_ADJ

Moran's I ADJ

I*pop_ PD

(λ = 5%)

I*pop_ PD

(λ = 50%)

I*pop_ ADJ

Local Moran's I

SaTScana


Local clusters

relative risk = 4

sample size = 30,000

Two adjacent neighbors

(Manassas City VA)

0.107

0.127

0.024

.079

0.056

0.060

+

0.973

Six adjacent neighbors

(Jackson County KS)

0.089

0.124

0.027

.087

0.042

0.047

+

0.962

Ten adjacent neighbors

(Fulton County GA)

0.081

0.125

0.030

.079

0.043

0.055

+

0.979


Global clustering

relative risk = 1.5

sample size = 5.000

Linear

0.997

0.285

0.232

.884

0.996

0.119

+

0.737

Exp

0.998

0.291

0.235

.886

0.997

0.129

+

0.781


a for global clustering evaluation, we used 50% of total population as the maximum search window. With the outlier detection, we use 5% of the total population as the maximum search window in SaTScan-E.

+ Power calculations are not available for Local Moran's I due to the fact that a statistics is produced for each geographic unit in the study. It is difficult to define power in the presence of multiple comparisons.

Jackson et al. International Journal of Health Geographics 2009 8:55   doi:10.1186/1476-072X-8-55

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