GMAT Strategy

I have the worst study habits ever, so I figured I would simply take a lot of practice tests to prepare for the GMAT. So I started taking them a few weeks ago and scheduled my test date for May 31st. I've been taking practice tests, but have been unhappy with my score (am aiming for at least 710). I was thinking about postponing my test date based on my low scores, but I took the mba.com test today and did much better than I expected. I'm trying to decide whether it was a fluke and if I should still delay my test date ... I'm nervous because I don't understand how there can be such huge point swings! Here is my practice test history so far, in the order that I took the tests:

Princeton Review CAT - 690
800score.com Test #1 - 700
Kaplan Paper - 720
800score.com #2 - 640
Manhattan GMAT - 640
800score.com #3 - 660
mba.com #1 - 770

So I'm looking at a massive, 130-point swing! In particular, I took those last three tests on consecutive days (Saturday, Sunday, and tonight).

I'm going to do a lot of studying between now and the test either way, but should I postpone my test date? These massive swings are scaring me and making me think that the 770 was a total fluke.

Any and all advice would be appreciated!

The massive score swings would hold IF the source of the tests were all the same. In your case it isn't. You've been getting lower scores, and rightly so, on the tougher tests. A 100 point swing is about normal on the tests. If you take the Kaplan CBT tests you should see the same swings if not worse. So relax, you are getting there.

Though honestly, i probably wouldnt vouch for your method of only taking tests to prepare for the GMAT

I am of the opinion that the algo of gmat is not GOD. It does have a standard error. (I am not referring to the one mentioned in the test report, that is standard deviation).

CAT algo is an approximating algorithm where it tries to best gauge your ability. It can make errors. So, one off test scores of 770 may not tell you much unless you take it a few times (new tests) and get a similar score.