The Scholastic Aptitude Test, the most widely used college entrance examination, will be revised to better measure critical thinking and problem solving skills, the College Board announced yesterday.

The revised SAT will include longer reading passages designed to make students think more deeply about comprehension questions and it will reduce the number of multiple choice questions by requiring students to produce their own answers to some math problems.

An estimated 1.3 million high school students take the SAT each year. A competing test, the American College Testing Program (ACT), is popular in western states and was revised a year ago.

College Board trustees decided at an annual meeting in Boston against another proposal to add an essay section to the test, a change that Asian-American and Hispanic educators charged would be unfair to students who did not learn English as their first language. The trustees instead opted to create a new writing test as part of the achievement tests, given in individual subjects, that far fewer colleges require and are taken by only 350,000 students.

The SAT revisions will constitute the most significant changes in the 2 1/2-hour exam since 1974, according to College Board president Donald M. Stewart.

The trustees approved the latest SAT changes, scheduled for the spring of 1994, after three years of study, including reviews by a panel of 15 educators headed by Derek Bok, president of Harvard University, and David Gardner, president of the University of California system. During its deliberations, the panel considered persistent accusations of racial and gender bias in the SAT.

Stewart, who is black, denied the revisions were being made in response to the charges of bias. The board has consistently attributed the lower average scores of women and minorities to differences in preparation.

"The SAT has been in almost continuous evolution. It has never been set in concrete," Stewart said at a news conference.

Bok said one goal of the panel was "to make the tests conform more closely to the actual skills used in the classroom in our colleges." He said the planned inclusion of math questions that require students to produce an answer, for instance, underscores the importance of problem-solving skills and "tends to discourage the more trivial kinds of coaching."

The revised SAT will include 10 to 15 math questions that will require students to produce answers, reducing the number of multiple-choice problems from 60 to 40 to 45. The College Board also will allow students to use calculators, a practice commonly permitted at many colleges.

In the verbal section, there will be more reading comprehension questions and the passages on which they are based will be longer. One set of questions will involve two longer passages that take different points of view on the same subject.

In addition, 25 questions on antonyms will be dropped.

Similar math and reading changes will be made in the Preliminary Scholastic Aptitude Test (PSAT), which is taken early in high school and used to award National Merit and National Achievement Scholarships. Some colleges also use lists of top scorers on the PSAT for recruiting.

Gregory Anrig, executive director of the Educational Testing Service in Princeton, N.J., which administers the SAT on behalf of the College Board, said the scoring system will remain the same. The maximum score is 800 on each section on verbal and math skills, for a total of 1600.

The revisions did not appear to placate critics of the SAT, who have said that the tests are biased and inaccurate predictors of college success.

The National Center on Fair & Open Testing, a group opposed to standardized testing, dismissed the revisions at a news conference immediately after the College Board's.

"FairTest concludes that the new SAT amounts to little more than rearranging the deck chairs on an educational Titanic," said Robert Schaeffer, the group's public education director. "None of these changes address the SAT's real flaws."