How does the resolution of two raster images affect their correlation?

My question is a bit theoretical. Imagine that I have two raster files (raster A and B). Raster A has grid cell size of 1 km and raster B has grid cell size of 100 m. I would like to like to estimate their correlation. I could use ‘Band Collection Statistic’ in ArcMap and check the results of the correlation matrix. ‘Band Collection Statistic’ uses the maximum cell size of the input raster files. Therefore, in this case, it would be 1 km from raster A. If the minimum cell size was used instead of the maximum (i.e. 100 m) and upsampling took place for raster A beforehand (to convert 1 km to 100 m resolution), how different would the correlation be? Is it going to increase, decrease, stay the same and why?