Statistical Filters GroupLens [resnick et al 94, MiT Filters UseNet News postings Similarity: Pearson correlation Prediction: Weighted deviation from mean =ra+-∑(n1-rn) au8 Statistical Filters ◼ GroupLens [Resnick et al 94, MIT] ◼ Filters UseNet News postings ◼ Similarity: Pearson correlation ◼ Prediction: Weighted deviation from mean = +  −  a u u u i a Pa,i r r , r w , ( ) 1 