Three nights a week on the top floor of a downtown Baltimore Holiday Inn, a relatively random group of middle America comes together clutching invitations promising the bearers will play "an important role in television."

The people have been plucked in to preview and give their reactions to "two prerecorded typical half-hours of television"--as the invitation says--which Saturday night meant watching pilots for two typical sitcoms interspersed with ads and filling out questionnaires seeking the viewers' feelings about both the shows and the ads.

People, not knowing what to expect, came to the preview in their Sunday-go-to-church clothes: leisure suits, dresses, polished shoes. Several men wore dress suits, but there were few alligator or polo player shirts. Members of the audience had come from as far away as Washington and York, Pa.

They had been seduced by a generic-looking invitation they had received in the mail, which opened "Dear Televiewer" and proceeded, solemnly intoning: "If the shows are telecast, you will be able to feel that you were a member of the team that helped judge and evaluate them for their final release over television networks and stations."

If that wasn't sufficient inducement, a P. S. pointed out that "approximately $225.00 worth of prizes will be awarded during your preview." The P. S. did not say that the prizes were, among other things, feminine napkins, antacids, soft drinks, potato chips, air freshener, menstrual pain reliever and oven cleaner.

The months-long testing being done in Baltimore is not at all unusual. Indeed, as Saturday night's emcee Jeff Adams told the group of 125, testing of those same shows was going on that same night in four other cities: Boston, Houston, San Francisco and Detroit.

These tests of independently produced pilots and commercials are being conducted by an Evansville, Ind., firm called Research Systems, one of several firms that do such market research. The tests are contracted for by producers seeking to fine-tune their pilots before submitting them to the networks and by advertisers seeking to gauge the effectiveness of their television pitches.

The networks each spend several million dollars a year on similar testing, the point of which, as ABC vice president for research Roy Rothstein said, "is to really see what the strengths and weaknesses of the programs are, to see what the audiences like and dislike, to give us an indication if the show has any potential at all."

Entering the Roman Holiday Ballroom on the 12th floor of the hotel Saturday, one was handed a legal-sized, black plastic folder. A smiling young woman or man seated each group of would-be critics. The chairs were arranged around a center stand of four television sets, each facing outward.

The first task was to fill out a questionnaire. This involved expressing a preference for particular brands of soft drinks, potato chips, breakfast cereals, instant coffees, pickles, green chilies, toilet soaps, toothpastes, cough drops, stomach remedies, aerosol air fresheners and oven cleaners. Properly completed, the questionnaire qualified one for a chance to win "The Shopping Bag," which included one of each of the brand-name items the participant had indicated.

A man in green pants had trouble with the questionnaire. He skipped the air fresheners altogether, mumbling, "Air fresheners. Hmmph. I don't believe in them." He chose the only nonaerosol oven cleaner, explaining to himself that it was the perfect choice because "you get more for your money here 'cause there's no aerosol in it."

Evelyn Sharpe, a retired woman from Washington, had come with her daughter, Jean Weston, and two friends "to see what it's all about." Yes, she said laughing shyly, she watched a lot of television. She thought, having filled out the first questionnaire, that the previewing might have as much to do with the commercials as with the programs.

Charles Summers, 26, had come to Baltimore from York, Pa., with Tammy Decker, 18. "I've been into TV for a long time," Summers said. "I have hundreds of videotapes at home, mostly from the '60s 'cause there's such garbage on today . . . Now when I gripe about something, I'll have a reason. I'll have the right to complain."

After the first four Shopping Bag winners had been selected, Adams said the audience would see two shows and then be asked some questions about them. "We are not connected with the material you are seeing," he said. "You will not hurt our feelings with frank responses."

The first show, "The Ugily Family," featured Al Molinero as the head of a New Jersey family that moves to California and has trouble adjusting to the "California life style." There were a lot of jokes about "the ugly family," all of which were followed by Mr. Ugily's insistent, whining explanation about "the I, right there between the G and the L."

The episode was interrupted by commercials. When it was over, Adams led the audience through a second set of questions. First, about basic demographic data (age, sex, income, TV viewing habits). Then came 10 questions about the pilot: How much did you enjoy it? Would you like to see it as a weekly series? How interested in seeing it as a weekly series would you be, exactly? And so forth, right down to the key question: Did you think you would even be interested in watching a show based on the concept of a New Jersey family trying to adjust to the California life style?

The fellow in the green pants gave the show carefully considered, noncommittal reviews. He thought it "good," and said he "might possibly" be interested in seeing it as a weekly series.

The questionnaire finished, the lights were once again dimmed and the video recorder rolled on "Bumpers," a second sitcom, this one about a blue-collar worker in his mid-20s who worked on a Detroit auto assembly line putting bumpers on cars. As he explained it, "I put bumpers on cars, 10 hours a day. As soon as I get through with one, zoop!--there's another one. One bumper every 1 minute and 36 seconds."

The end of "Bumpers" brought two more questionnaires. There was one about product preferences, which again qualified one for The Shopping Bag. That was followed by a questionnaire about "Bumpers" almost identical to the one about "The Ugily Family," and then some general questions about the frequency of one's use of stomach remedies, air fresheners, green chilis and sanitary napkins. There was a page of questions about the testing itself (most critical, would you come to another of these TV previews?) and the session was over. People turned in their questionnaires as they left.

"Being here now gives me a right to bitch," Charles Summers said. Then he offered his opinions of what he'd seen. " 'The Ugily Family,' " he said, "will be a real success. A real hit. It's so awful! It's obviously aimed at the lowest common denominator." "Bumpers" was a little more problematic. Summers didn't think it would be an instant success, but said, "It was good. Given time and development, it could be a hit too."

Jean Weston was a little more skeptical. When asked what she thought, she smiled knowingly and rocked her left hand back and forth in the "so-so" gesture.

"I wouldn't come back," said Weston, shaking her head. "I'm a little doubtful about whether this is really for the shows. It seemed more like they were trying to sell products."

Weston said she "really liked" "The Ugily Family," but thought "Bumpers" was "too silly."

If a friend of hers received the same invitation, what would she advise? "If it's in Washington, what the heck, go. But if you have to drive, no way."