Federal managers and supervisors governed by merit pay got 11.5 percent average raises last year, while their subordinates got a flat 9.1 percent increase. Some of the Grade 13 through 15 chiefs got as much as 25 percent. A handful, who got bad report cards, got only 4.55 percent, half what their employes got.

So far eight federal agencies have made merit pay-outs to managers and supervisors. All departments must shift to it this year. It will put an estimated 125,000 employes in Grades 13, 14 and 15 under merit pay. Salaries for those grades range from $25,000 to $50,000.

Under the merit pay plan mandated by President Carter's civil service reforms, GS 13 through 15 personnel designated as managers or supervisors are supposed to be rewarded according to performance. People under the plan do not get automatic longevity raises, nor are they guaranteed the full amount of the October federal pay raise for other white collar aides. t

When all agencies shift to merit pay this year, thousands of supervisors and managers here will automatically get only half the October raise. To qualify for more, they must get good-to-superior marks from bosses. Last year rank-and-file U.S. workers got a 9.1 percent raise. But in merit payouts made in eight agencies -- covering just over 2,100 managers and supervisors -- the average pay raise was 11.5 percent.

About 7 percent of the supervisors and managers got the minium increase of 4.55 percent or amounts up to 9 percent. Nearly half of the group (49.5 percent) got from 9.1 percent to 11.5 percent; 30 percent got increases ranging from 11.5 percent to 14.5 percent. More than 13 percent of the people under merit pay got raises of from 14.5 percent to 25 percent.

Money to finance merit pay pools comes from funds that would have been used to give regular raises to those workers, plus money saved by denying them regular in-grade raises for length of service. The eight agencies that have made merit pay raises are Small Business Administration, Civil Aeronautics Board, portions of Environmental Protection Agency, Farm Credit Administration, Office of Personnel Management, Selective Service, U.S. Metric Board and the Civil Rights Commission.

All federal departments will shift to merit pay this year for designated GS 13 through 15 supervisors and managers.