MGCAT vs. Kaplan vs. GMATCLUB

Hi All...

I was taking all those CATs & my scores vary quite a bit...

Any idea/comment?

MGCAT1: 670 (Q46 V35)
MGCAT2: 710 (Q51 V36)
MGCAT3: 670 (Q46 V35)
Kaplan1: 720 (Q51 V35)
Kaplan2: 760 (Q51 V42)
Kaplan3: 750 (Q51 V42)
GMATCLUB1: Q51 V38 ~730
GMATCLUB2: Q51 V40 ~750
GMATCLUB3: Q51 V35 ~720
GMATCLUB4: Q51 V39 ~740
GMATCLUB5: Q51 V46 ~770?

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