The computer did it, claimed the president of Wharton Econometric Forecasting Associates. He was talking of the perfect timing of the party they threw just one day after the glad tidings rang forth concerning the awarding of the Nobel Prize for economics to the chairman of their group, Lawrence R. Klein. Just another splendid example, he said with a modest, self-deprecatory chuckle, of economists' uncanny ability to forecast events accurately.

Actually the bash at the International Club had been arranged some months beforehand to introduce the newly formed Economic Policy Analysis Group within the company, but all that was immediately over-shadowed by the news of the new Nobel laureate, who stood within a respectful pool of colleagues, former students and other well-wishers, whose response to his award was as enthusiastic as his was self-effacing.

The award, said Klein, was a vindication of sorts. People in the social sciences are generally subjected to the sort of abuse best represented by Sen. Proxmire's penchant for announcing his prizes for what he considered gratuitions and irrelevant research at the government's expense, Klein said at a press conference before the reception. The Nobel Prize, he thought, was a rather neat way to send the good senator a message "not to strangle social science research through his Golden Fleece award."

Klein, or "Special K" as he was referred to by one former student with a reputation for wit, is a soft-spoken, modest man with a diffident, professorial manner. He expressed the requistie joy at the honor conferred upon him and said he had received congrations from yet another well-wisher this afternoon, when Jimmy Carter called him from Air Force One. He still advises the president from time to time, he said, a role he began during Carter's first presidential campaign, but this conversation "was mostly chitchat."

Whatever passes for chitchat between president and Nobel Prize-winner remains a mystery at this writing, but the chitchat at a party given by and for economists, half of whom are there fishing for government contracts to predict God-knows-what and the other half of whom represent the government agencies that qualify as the catch of the day, is murky business indeed.

We are talking, after all, about conversations between practitioners of what has long been known as the dismal science. To try and discover here whether the Iran-Iraqi war is going to cause a 13 percent reduction in the GNP would be a futile effort at best. Little sense if any was to be made of angst-ridden snatches of conversation such as the following: "We've got the data base! We've the models! If only those people had the proper zeal!"

Still, there was a respectable dander to be gotten up whenever it was mentioned that there were those in the general populace who place the predictions of economic forecasters somewhere between the methods of Merlin and the local weatherman on the credibility scale. "Forecasting is imperfect, you're damn right it's imperfect," said F. Gerard Adams, professor of economics and finance at the University of Pennsylvania and a longtime colleague of Klein's. "These models are like violins, you must tune them constantly and constantly practice them." But yes, economists "have had a tremendous impact," particularly if you look at the difference between the prewar and postwar economies.'We've had problem with inflation, sure, but have we had a depression? No. Have we had anything like the problem then? No. We're in much better control than we ever were."

And yet, it might be worth bearing in mind the words of one sober-suited sage, making his solemn way among the hors d'oeuvers and the distinguished company. "In this business," he said, "I've found it pays to be very humble."