the minimum feature number of spatial autocorrelation analysis (Moran's I)

Discussion created by j269li on Oct 16, 2013

I am trying to use Moran's I test statistic to measure the spatial autocorrelation of soil properties(e.g., soil organic carbon).

I checked ArcGIS resource Online to see how Global Moran's I works, and the "Best Practice Guidelines" says that "Does the Input Feature Class contain at least 30 features? Results aren't reliable with less than 30 features". So my question is why the number 30 is chosen as the threshold or the optimal feature number?

Thank you!