Karen Chambliss is 28 years old, an aspiring doctor and a first-year student at Georgetown University Medical School who believed for years that her only chance to attend a top-notch school was by winning a National Health Services Corps (NHSC) scholarship.

Chambliss had good reason to believe that this year she would win the scholarship, which is part of a federal program that pays for a student's medical education in exchange for an agreement to practice in a medically underserved urban or rural community. Her first year at school was financed through a different federal scholarship program, one whose recipients receive priority consideration for the longer term NHSC awards.

"Now I feel like my career is on the line," Chambliss says. The reason is a 145-page document nicknamed "the Black Book."

Prepared by David Stockman, director of the Office of Management and Budget, and his staff, the book contains a list of programs the Reagan Administration would like to cut or eliminate. The National Health Service Corps Scholarship Program is one of them.

Under Stockman's proposal, all new NHSC scholarship awards in 1981 and 1982 would be eliminated. The cuts, according to the book, would save about $3 million in fiscal 1981 and $14 million in fiscal '82.

For Karen Chambliss, President Reagan's budget cutbacks mean she will probably have to find another way to pay for her medical education. For others in the Washington area the impact will be different; the cutbacks will mean less food in the supermarket, less music in their lives or a newspaper that comes two days late. The range of people potentially affected by the cuts, in fact, is a testament not only to Reagan's determination to reduce the deficit, but to the myriad ways that federal money reaches into people's lives.

A clearer idea of where the cutbacks will occur is expected to come Wednesday night when President Reagan speaks to Congress, but the final shape of the reductions will be determined only after a bitter political fight. In the meantime, people like Chambliss wait for the budget ax to fall. The following is a look at a half dozen men and women whose lives could be changed in the next few months. THE WELFARE MOTHER

Linda Green, 32, is tall and overweight. Her doctors have been telling her she should lose at least 25 pounds and stay away from spaghetti and french fries.

Green, of 601 edgewood St. NE, says she would like to follow their advice but cannot afford it, even with food stamps.

"You can't buy lean cuts of meat when you and your daughter have to live on $100 a month of food stamps," she says. "Of course I buy spaghetti and potatoes."

Green and about 22 million other Americans will be buying less food with food stamps if President Reagan's proposals are approved by Congress. Under Reagan's proposals, gross income rather than net income would be used as a standard of eligibility, the cost of school lunches would be deducted from the food stamp allotment, and everyone would receive fewer food stamps.

For Green, the proposals mean that she and her 12-year-old daughter would receive only $80 worth of food stamps a month, instead of $100. Her only other income is $225 a month in public assistance. Of that money, she spends $109 a month for rent for her one bedroom apartment. The balance is for the telephone bill, household items like toothpaste and shampoo, and clothes for herself and her daughter.

But she's not ready to give up.

"I'm going to survive," she says. "Food stamps or no food stamps." THE SYMPHONY DIRECTOR

One of the best things about being the managing director of the Fairfax Symphony, says Barbara Serage, is seeing the delight in the eyes of school children as the orchestra's harpist glides out on roller skates, and tunes up the harp with a roller skate key.

The mysterious compatibility of roller skates with one of the most beautiful instruments of classical music was something 4,300 elementary students learned last year in the symphony's chamber music program.

"We've gotten stacks of letters saying this is the best thing that ever happened to the school," says Serage, who was hoping to extend the musical introduction to junior high students but now fears the program may have to be eliminated altogether if the proposed 50 percent cutback in the budget of the National Endowment for the Arts come to pass.

Of the symphony's total budget of $180,000, 41 percent comes from private contributions. The NEA, through the Virginia Commission for the Arts, provides the symphony with $16,000, of wich $2,000 goes to support the programs of the 35-piece chamber orchestra, and $14,000 goes to support the 116-piece symphony orchestra.

Sitting in front of her thermometer graphs, which show the mercury on the fundraising index only a little above the bulb at the bottom, Serage says she tries not to get depressed. "If you got depressed about everything that went wrong you'd go out and shoot yourself," she laughs. "But I sit here and look at them and worry." THE CETA WORKER

Last March, Jocelyn T. Bynum, a graduate of Burdick Vocational High School in Northwest Washington, got a job in the District government's department of communications under a federal manpower program -- the Comprehensive Employment and Training Act -- that is one of the main targets of the Reagan Administration.

Bynum joined the city for an 18-month job training stint, then took three months' maternity leave last summer. She had hopped to make up for the three missed months by extending her stay through December of this year -- until Reagan announced his plans to eliminate the CETA program.

Now Bynum has until September to find a permanent job, so she can support herself and her two children, two-year-old Shannita and the baby, Stanley, born last September. The alternative, she said, is returning to the welfare rolls, something she said she is determined to avoid.

"I was on welfare and I don't want to go back on there," she says, looking at the desk photograph of baby Stanley smiling boldly, propped up on a pillow. "It would mess me up completely if they just cut it, just like that." He (Reagan) said he wants the young people to work and get off welfare. How could they work if you cut out the program that trains them?" THE COLLEGE STUDENT

Each month, Welmoed Bouhuys, a 20-year-old sophomore at George Washington University, receives a $336 Social Security check.

Bouhuys receives this benefit under a special Social Security program designed to pay the expenses of college students whose parents are either dead, disabled or retired. Bouhuy's father fied in June 1979, three months before she began her freshman year at GWU.

But Bouhuys' father, a professor at Yale University, left a $50,000 trust fund for her education, and she also receives $1,500 a year from Yale, under a scholarship program for the children of that university's professors.

Bouhuys acknowledged she could pay for her schooling without the Social Security benefit, but, she said, "it makes my life easier."

Although Bouhuys' case may not be trypical of most students receiving Social Security benefits, her example demonstrates what can happen in a student aid program that is not based on need, and why the Reagan Administration wants to abolish it. THE STEELWORKER

Alan Fisher hasn't been called in to work his job as an electrician's helper at the Bethlehem Steel plant outside Baltimore since last May. He has house payments, and a baby coming in the summer, but the worries that dog him have to do with pride and disillusion and politics as much as money.

When Fisher had work he made $400 a week. Now for a limited time he gets a weekly unemployment insurance check of $120 and $140 in federal Trade Relief Assistance benefits, a program that President Reagan wants to cut.

The federal government in 1981 will pay our $2.7 billion in TRA benefits to 500,000 manufacturing workers who owed the loss of their jobs to imports. Most of the recipients this year have been auto workers, but workers in the steel industry, laid off because of the increase in imported steel, have also benefited.

Fisher's income will be halved next month when his TRA runs out, regardless of cutbacks Reagan may make in the program. After that, in June when his unemployment expires, things look even bleaker. For the time being, "it's a matter of doing things differently," he says. "I'm luckier than a lot of guys, I don't have a big house payment and my wife works."

Fisher sees the proposed scale back of TRA perhaps more philosophically than many of his co-workers. "TRA was set up to keep us from revolting against the corporations. It protects us from the workers' rage," he says."I don't want to lose the money, but I don't buy the fact that I'm getting it because of foreign imports. The problem is with the fact that the corporations are pulling money out of steel and putting it into other things. I don't want TRA, I want my job." THE PUBLISHER

In the 20 years since Jack McMullen joined the Cumberland News and Times, he has watched the circulation of this small daily in the rolling hills of Western Maryland inch slowly upward by about 3,000 copies.

Now McMullen is faced with the prospect that 6,000 of the paper's hard-won Saturday circulation could be "loped off just like that."

The circulation, McMullen fears, might be lost if the Postal Service eliminates Saturday mail service, a possibility raised by OMB director David Stockman's proposed budget slashes.

Distribution of small papers like McMullen's often depends as much on the postal truck as the circulation truck, with readership fanning out miles from the paper's offices. Indeed, the Cumberland News and Times is in a better position than most. Only about 6,000 of the 35,000 copies it sells each day go out by mail.

Still, McMullen is concerned. "It takes too long to build up circulation to see it lopped of quickly," he says.

Because this isn't the first time the threat of Saturday cuts has come up, McMullen already has looked at other ways of getting those papers out. And he was heartened last week to hear that Postmaster General William Bolger said that even with Stockman's proposed cuts he has no plans to elilminate Saturday service.

Still, if the time comes, McMullen is ready to fight. "Elimination of Saturday service would not be totally disastrus to my paper," said McMullen. s"But it would certainly hurt."