February 16, 1981

Despite surprisingly steady business signals in January, many corporate economists expect sluggish economic activity in the United States through the first half of 1981. But they see the economy picking up in the second half, building toward a robust 1982. While most rousingly endorse the combination of Federal budget reductions and tax cuts for businesses and individuals that President Reagan is expected to propose Wednesday, they stress that such a balm for past economic wounds will not work much cure for several months. The economists say that Federal Reserve Board policy toward interest rates and money supply growth will play a large role in determining the path of the nation's economy for the rest of the year.

While Adelphi University students mourned a classmate who was shot and killed yesterday by a Garden City policeman, the Nassau County police said that a grand jury investigation of the shooting would begin this week. As students gathered today outside the Ruth S. Harley University Center, several disputed the police version of the incident. They said they hoped the grand jury proceeding would clarify what had actually happened. According to the county police, the officer, John McNulty, fired his revolver after Edward Fonseca grabbed his blackjack and lunged at him. The .38-caliber bullet severed two of Mr. Fonseca's arteries, pierced his liver and then came to rest in his stomach. He died three hours later at Nassau Hospital in Mineola.

Vice President Bush and some key members of Congress urged support today for the budget package that President Reagan plans to present to Congress Wednesday, but representatives of groups fearing that they could be hurt urged caution in reducing government spending. Saying in New York that the Federal budget had too much ''fat,'' Mr. Bush added: ''We can and will be able to reduce the heavy burden of taxation on our people - taxation that stifles industrial growth and individual initiative.' And Senator Pete V. Domenici, Republican of New Mexico, chairman of the Senate Budget Committee, said that Mr. Reagan's proposals would bring inflation down to ''a reasonable level'' by 1984 if Congress approved the President's whole package of $48 billion in cuts in this fiscal year and the next. Opposes 'Piecemeal' Work ''The real test will be whether it can be kept together during the legislative journey,'' Mr. Domenici said. ''It is important that it not be cut up piecemeal by various Congressional committees.''

The chairman of a committee of the Taxi and Limousine Commission that this week will consider a 50-cent surcharge for nighttime taxi rides in New York City said yesterday that the charge would not be approved unless the commission could obtain accurate income reports from all segments of the taxi industry. The committee chairman, Marvin Greenberg, said the financial records would have to be reviewed and public hearings would have to be held. He said it would be at least several weeks before the full commission would act on the surcharge proposal.

''When you start manipulating a system that treats three million people a day you'd better be a little careful before jumping off the cliff.'' - Dr. James H. Sammons, executive vice president of the American Medical Association, speaking of proposals to cut Medicare and Medicaid. (A12:3.)