Source: Miami Bridge
This is a convention that allows you to arrive at a better contract when your partner opens 1NT and you have a hand with 0-7 points and 4-4 or better in the major suits. In regular Stayman you would be forced to pass. Using this system, you can probably do better even if you have a balanced hand.
When the bidding proceeds:
1NT – 2
2 – 2
it shows a bad hand and asks partner to “pass or correct” usually arriving at the 4-3 fit or better in the appropriate major. Responder can also use this method when he is 3-4-1-5. If opener bids 2 or 2, you can pass happily. When partner bids 2, you can bid 2. Partner will think you are 4-4 in the majors and bid 2 with three spades and two hearts. You can then bid 3, assured of an eight-card fit.
After studying computer analyses, it becomes apparent that you should almost always remove from 1NT with any hand that is 4-4 or better in the majors and fewer than eight points. There are only a few hands that play better in 1NT. It seems the more points (up to seven) that you have and the more points you have in the minor suits, the more likely you will do well in 1NT. For example, if you held:
you would be better placed to pass 1NT. In general, however, if you always were to remove 1NT, you would be correct 57% of the time. If your partnership opens 1NT with a five-card major that number goes up.
The bottom line is that to avoid taking out the trash use Garbage Stayman.