GMAT vs Manhattan CAT

[chakraborty.subhabrata]

Can anybody guide whats the standard difference between Manhattan CAT available online & Real GMAT?

I have scored 630 [46Q,30V] in MGMAT CAT, where as my target in 700 in Real GMAT....
I want to know is this close?

[StaceyKoprince]

The standard deviation as measured from our students' final practice test to their real official test is 50 points. (The standard deviation on the real test is about 30 points.)

In calculating that figure, we include all student results; we don't check whether the student took the practice under 100% official conditions. As a general rule, IF you took the test under 100% official conditions, then the number is fairly accurate for a standardized test, which means within maybe 40 points in either direction. If you did not, the score is not as valid, and it might be inflated a bit depending upon how you deviated from official conditions. Skipping the essays often (though not always) leads to an inflated score. Pausing the test and continuing to work on a problem on your scrap paper almost definitely leads to an inflated score. Taking much longer breaks than allowed also often leads to an inflated score.

The short answer: you're not too far away from your goal, but you do have a ways to go. If you took the test under 100% official conditions (including the essays), then you've got roughly 70 points to go (again plus or minus the error). If you took the test under conditions that would likely inflate a score, then you may have a ways further to go.