The number of first-year students in the Law School choosing pass-fail grading declined this year from 22 per cent to 15 per cent of the first-year class, a preliminary survey showed yesterday.

But many observers feel that the decline does not indicate a dropping off of student interest in pass-fail grading, but is instead due to a new, complex method through which students choose their grading status.

Under the new method a student can say he will accept pass-fail grading if a certain percentage--which he specifies--of the first year class also decides to go pass-fail.

Thus, on a form distributed to first-year students earlier this week, a student could have stated that he would choose pass-fail grading on the condition that 50 per cent of his classmates also do so. A student could also choose pass-fail grading unconditionally.

The adoption of the new method followed a student protest last week which called for mandatory pass-fail grading for all first-year students. The protest concerned only first-year grading because the first year is generally acknowledged to be the most difficult and pressured of the Law School's three-year program.

In response to the protest, a student-faculty committee designed the new method for choosing pass-fail grading and expected the method would result in an increase in the number of students choosing pass-fail.

Laurence H. Tribe, professor of Law and one of the designers of the new method, said yesterday that the preliminary statistics, which indicated a decline in the number of people choosing pass-fail, are not final. Students may decide to choose unconditional pass-fail grading until next Friday.

"It's premature to make any judgment," Tribe said. "Some people are waiting to see what happened before deciding what to do."

At a meeting Tuesday, the Law Faculty passed a resolution, proposed by Tribe and Louis L. Jaffe, Byrne Professor of Administrative Law, which called for a complete review of the School's grading system.