In a show of leniency apparently intended to counter criticism of human-rights violations, a military appeals court today reduced the prison sentences of 11 Iranians convicted last month of subversive activities.

The verdicts, which has been anticipated, came after a two-day appeal hearing. Some foreign observers, said the outcome appeared to have been decided before the 10 men and one woman appeared in an unusual public trial.

The defendants, all but one of them university-educated appeared calm and even bored during the appeal, as they had during their trial a month ago.

Looking relaxed, they joked in an anteroom before today's session. In court, they showed no reaction as a reader announced reductions in the sentences of three men from life to 10 years and cuts by generally more than half in the terms of the others.

Eight of the defendants immediately told court officials they would appeal the verdicts further. Shah Mohammed Reza Pahlavi must rule on whether new appeals can be made. If he approves, the case will go to Iran's Supreme Court.

Some foreign observers said the show of leniency was largely cosmetic rather than a signal of any profound change in Iran's treatment of political prisoners. Secretary of State Cyrus Vance is scheduled to visit Tehran starting Friday.

So far, the Carter administration has avoided any comment on human-rights violations in Iran, a major purchaser of U.S. Military hardware and considered strategically important.

Defense arguments, in both the trial and the appeal, mainly included pleas for mercy combined with confessions of guilt by association with Communist and leftist groups. The defendants all claimed to have been led astray by foreign elements hostile to Iran.

Their confessions were first made during pretrial interrogation by SAVAK, the feared Iranian secret police. Neither the military tribunals nor the court-selected defense lawyers ever tried to determine whether the confessions, on which the initial guilty pleas were based, resulted from threats, fear or coercion during the interrogations.

A local newspaper said the prosecution's evidence against the defendants also included "investigations by SAVAK into their activities in Iran and abroad." This confirms earlier reports of surveillance by SAVAK agents in the United States and Europe, where most of the accused studied.

Foreign legal observes during last month's trial said, after interviewing the defendants, that none had ever received the charges against him in writing. Some were either not informed of the law under which they were accused or not allowed to see a lawyers for weeks or months after ehy were arrested late last year.

Observers at the trial, including two lawyers from Britain and the United States, said they felt that several aspects of the case amounted to human-rights violations