Table 2. Detailed statistics of datasets.

Rating grade	Number	Number of users	Number of books	Number of ratings	Children’s books age (3–5 years old)	Children’s books age (6–8 years old)	Children’s books age (9–11 years old)
Dataset 1
5 star rating	1,204	1,001	856	948	496	551	157
4 star rating	1,041	978	862	1,002	381	406	254
3 star rating	674	535	524	456	371	151	152
2 star rating	346	265	250	216	108	148	90
1 star rating	245	135	89	103	76	80	99
Dataset 2
5 star rating	1,309	976	847	168	456	541	312
4 star rating	962	958	916	924	318	275	333
3 star rating	609	456	507	416	297	346	112
2 star rating	474	311	301	297	98	134	242
1 star rating	292	154	117	97	145	55	92