Steve Stone was pitching poorly at the start of the 1979 baseball season, so he decided to take some action. The Baltimore Orioles' star shaved off his mustache, changed his number from 21 to 32, installed a lucky stuffed sheepdog in his locker, switched gloves and bought new shoes.

His game improved radically, and the team went on to play in that year's World Series.

Before each home game, Stone, 33--who considers himself "pretty superstitious"--eats breakfast at the International House of Pancakes, accepts a rose from a friend, drives to Memorial Stadium via Charles Street , stops for a chocolate shake at McDonald's and listens to a tape of Jackson Browne and Hall and Oates.

"It's part of my winning formula," says the 1980 Cy Young Award winner. "Everything about the routine is associated with winning. Several years ago a sportswriter took me to breakfast at the pancake house, and I won 13 straight games. A woman friend brought me a rose, and I beat the Yankees.

"It's fun, it puts me in good spirits and it gives me something to do during the day to keep my mind off my performance."

Superstition, say the experts, is a human attempt to impose order and certainly on a chaotic, uncertain situation--be it ball game, court case, job interview or exam.

"It's a form of magic," says anthropologist George Gmelch, "that attempts to bring about a desired end--like winning--by using a means that bears no logical relation to that end, like a lucky penny.

"And in technologically-advanced societies that pride themselves on a scientific approach to problem solving, rituals of magic are common."

Athletes are among the most superstitious groups, says Gmelch, 35, who played first base with Detroit Tigers' farm clubs for three years. (He ate chicken every day at 4 p.m. and kept his eyes closed during the national anthem in an effort once to prolong a bating streak.)

"A professional athlete's livelihood depends on how well he performs. Practicing a superstition can help reduce that anxiety," says Gmelch, now as assistant professor at the State University of New York at Albany.

"A lot depends on the player's self confidence, and a superstitious belief has a psychological function. The magic obviously does not make a pitch travel faster, but it may give the player a sense of control."

Performing artists--whose jobs also involve uncertainty and require self-confidence--also tend to be superstitous. Actress Mary Steenburger has earned an Oscar nomination for her supporting role in "Melvin and Howard," but refuses to write an acceptance speech because she feels it would be bad luck.

ABT prima ballerina Natalia Makarova will not let anyone but herself or her personal assistant handle her toe shoes so they don't touch the floor.

"Once in California a friend was carrying an entire bag of Makarova's shoes into the theater and accidentally, dropped them," recalls assistant Deana Makarova (no relation). "There was a big rush to get a new pair of shoes, have ribbons sewn on by hand and have them broken in so she could dance 'Swan Lake.'"

The reason actors, dancers and athletes are superstitous, says Redskins' quarterback Joe Theismann, "is because they're all entertainers. A lot of the job has to do with how you feel and getting in a good frame of mind to go out and do your best."

Theismann's superstitions include eating a banana split (chocolate, vanilla and strawberry) the night before a game and taking his clothes off in the same order (shirt, shoes, socks, pants)--a pre-game ritual he's been following since college. His latest is neatly folding his hand towel when he's on the sidelines and clutching it until he goes back on the field.

"During a Giants game a couple of years ago we were doing lousy," he recalls, "and I remembered that I didn't put my shoes in the right place (right front corner) in my locker.

"During half-time I went into the locker room and put them in the right place. We won in overtime."

The Madison Hotel, like many high-rise buildings, has no 13th floor. Builder Marshall B. Coyne says he's not superstitious himself, but guests often are.

At the Washington Hospital Center--which does more surgery than any other hospital in the District--the operating room schedule is lighter than usual for today.

"When scheduling a patient for elective surgery I always asked if they had any problem being scheduled for Friday the 13th," says Dr. Harold Hawfield, a former surgeon and now the director of medical affairs.

"Some patients do and some don't. Some even wanted to check their horoscope. There's always anxiety associated with surgery, and you wouldn't want to put a patient in an uncomfortable emotional situation."

Some people's superstitutions have led them to believe that President Reagan is "the devil." Believers in numerology--particularly the notion that 666 is the most "evil number"--point out that the Maryland Lottery's winning number on election day was 666 and that each of his three names contains six letters: R-o-n-a-l-d W-i-l-s-o-n R-e-a-g-a-n. (The White House press office denies this allegation.)

Seventy percent of 450 college students surveyed employ "magic," according to a study by anthropologist Gmelch and Richard Felson.

"Students use both productive magic--like carrying a good-luck charm to an exam," says sociologist Felson, "and protective magic--like crossing one's fingers to ward off danger.

"Most students seemed to be at least intellectually aware that it does more to reduce anxiety than bring about favorable results, but preferred to play it safe. They aren't sure it works, but they aren't sure it doesn't work either."

The three basic kinds of superstition, says Gmelch and Felson, are taboos, fetishes and rituals. A taboo involves avoiding an action that might bring bad luck, such as baseball players' deliberate effortnot to step on the foul line when they take the field.

A fetish is a lucky charm--like a rabbit's foot--believed to embody supernatural powers that aid or protect the owner. Rituals involve a "magic routine' that may be cultural--wishing on birthday candles or the evening star--or personal.

Personal rituals (like pitcher Stone's) often are based on the same principle demonstrated by behaviorist B.F. Skinner's pigeons, says psychologist Patricia Rothstein Dashefsky, whose doctoral thesis at George Washington University was on superstition.

"In the laboratory you see a direct link between response and reinforcement--a pigeon taps a bar and gets food," she says. "Outside the laboratory the relationship isn't always so clear. If someone performs a behavior and reinforcement shortly appears, that behavior is likely to increase."

So if someone scratches his armpit and then hits a homerun, he may associate one act with the other and start scratching his armpit every time he's at bat. If that person has high prestige--say a Babe Ruth--others may initate that behavior, even if they don't know how it started. This, Dashefsky says, may be how cultural superstitions are born and passed on.

"When you have a good performance," notes quarterback Theismann, "you try to figure out what it was you did that was so different or special. One time, you think, may be just coincidence.

"But if you try it again, and it works, it becomes a superstition."