Moran's Index in ArcGIS is different from in GeoDa

[ChangBoorn]

I recently need to calculate Moran's Index in ArcGIS 10.2. However, I found that the results in ArcGIS and GeoDa were different. My spatial weight matrix was 4-nearest neighbors matrix. And I also found that as the number of nearest neighbors increasing, the difference would increase. I guess this is because of projected coordinate system, but I don't know which result is correct. Anyone who can tell me? If the result of GeoDa is correct, how can we correct the calculation in ArcGIS? Thank you so much!!

[DanPatterson_Retired]

projected coordinates are best and the formulae for the global Moran's I is here so short of comparing the default values used by both you don't have a fair comparison unless you know what they are. Step back and look at the assumptions.  Also, if you are using geographic data in the other package, ensure that they return chordal distances like ArcMap does (at least that is the case in recent versions) To make sure everything is equally compared, only use projected data as inputs with the exact same parameters.