Effect of Collaborative Recommender System Parameters: Common Set Cardinality and the Similarity Measure

Table 2

Results classification according to the rating mean groups.

Sequence of users	Similarity measure	Sequence of similarity values	Maximum difference
→ → →; (high mean group)	PCC	1 → 0.707 → 0.451 → 0.612	0.549
	COS	1 → 0.987 → 0.975 → 0.973	0.027
	MWD	1 → 0.75 → 0.6 → 0.625	0.4
	MMD	0.75 → 0.64 → 0.485 → 0.536	0.265
→ → →; (low mean group)	PCC	1 → 0 → 0.311 → 0.512	1
	COS	1 → 0.949 → 0.937 → 0.922	0.078
	MWD	1 → 0.75 → 0.7 → 0.5	0.5
	MMD	0.444 → 0.375 → 0.4 → 0.3	0.144
→ → →; (medium mean group)	PCC	0 → 0.707 → 0.236 → 0.369	0.707
	COS	1 → 0.981 → 0.914 → 0.927	0.086
	MWD	0.5 → 0.75 → 0.5 → 0.5	0.25
	MMD	0.444 → 0.688 → 0.5 → 0.45	0.244
→ → →; (opposite-minded group)	PCC	−1 → −0.99 → −0.86 → −0.92	−0.14
	COS	1 → 0.759 → 0.727 → 0.681	0.319
	MWD	−1 → 0 → 0 → −0.13	−1
	MMD	− 0.89 → 0 → 0 → −0.12	−0.89