What was going on when I was born?

Economists, mortgage bankers and other housing industry analysts yesterday sharply criticized the Reagan Administration's plan to sell the Federal Housing Administration to private bidders by the end of 1989. ''If you're going to sell the F.H.A., you're effectively selling the American homebuyer down the river,'' said Warren Lasko, executive vice president of the Mortgage Bankers Association of America. Created by the National Housing Act of 1934 to combat the effects of the Depression, the F.H.A. has provided mortgage insurance to more than 51 million homeowners, enabling many to receive mortgages they otherwise would not have been able to obtain. The agency made a profit of $9.4 million last year.

A Spanish-language television station signs off for the night with a ''buenos noches.'' Then the studio technicians, all young people of Hispanic origin, discuss the next day's schedule. In English. A Harvard-educated bank executive, newly arrived from Boston, spends his first weeks studying the Spanish language and Hispanic history. The bank president, also a non-Hispanic, goes to a dance studio after work to learn salsa. A Georgia-born secretary rattles off a list of employees attending an insurance company picnic. ''Dominguez . . . Guerrier . . . Gutierrez . . . Santiesteban . . .'' she calls out without a hitch, accenting each syllable correctly, before stumbling upon a Polish surname.

IN completing a lost weekend, the Giants were unable to do what the Jets were unable to do - win a big game that would have simplified their status in the Super Bowl XX playoffs. And when somebody mentioned to Phil Simms after the 28-21 loss to the Dallas Cowboys yesterday that ''people say the Giants don't win the big game,'' the blond quarterback's face flushed in anger. ''People say, people say,'' he blurted, punctuating his words with obscenities. ''I'm proud of myself and the team. I'm tired of hearing the Giants can't win the big game.''

Every so often, Victor Harris, the president of Max Factor's Japanese subsidiary, is pressed by his American supervisors to attack the weaknesses of the Japanese cosmetics giant, Shiseido. But he says: ''I've spent a career examining their weaknesses, and you're not going to find any major ones.'' Mr. Harris, whose company is a leading foreign cosmetics concern in Japan, gives Shiseido top grades in marketing, production, quality and management, all of which have helped to push the company to the top here. Last year, Shiseido had sales of $1.5 billion.

''Is this some sort of tradition?'' asked Malcolm Blair, an Englishman, peering down into the skating rink at Rockefeller Center yesterday. ''I'm from Brooklyn,'' replied Lila Wood, ''I have no idea what this could be.'' Thousands of shoppers and sightseers jamming midtown yesterday crowded around the rink to behold the Yuletide spectacle of 300 tuba-bearing revelers walking gingerly on the ice beneath Prometheus and the Christmas tree to play a Christmas concert. The tuba enthusiasts have performed this ''TubaChristmas'' every year since 1974, and although it may not be in the class of the ''Messiah'' or ''The Nutcracker'' yet, in America, 12 years straight is a tradition.

Lauren Markoe, a senior at Bronx High School of Science, struck Amherst from her list of colleges because it flunked the sneaker test. ''Everybody at Amherst had on Nikes,'' she said, recalling a recent visit to the campus. ''If all the kids at a college are wearing the same expensive, brand-name sneakers, it's a sign that they are too interested in looks and materialistic things. I'm looking for people who are interested in other people.'' Gillian Salton, a senior at the Horace Mann School in the Bronx, ousted Oberlin from her list on the basis of locale. ''I thought, really, how would I like to spend four years 35 miles outside of Cleveland with 1,500 other people?''

Israel announced today that, in the last three weeks, Syria had stationed a variety of surface-to-air missiles along its border with Lebanon. Israel said the deployment seriously threatened regular Israeli reconnaissance missions over Lebanon. Israeli military sources said the Syrian move - which Israel said began soon after Israeli jets shot down two Syrian MIG-23's in Syrian airspace on Nov. 19 - constituted a ''dangerous change in the status quo.'' Any Israeli plane flying over Lebanon will now be exposed to Soviet-made SAM-2, SAM-6 and SAM-8 surface-to-air missiles, the military sources said. Before three weeks ago, the Syrians had no SAM-2 batteries near the Lebanese border and far fewer SAM-6's and SAM-8's in that area, the sources said.

A report in the Briefing column of the Washington Talk page on Nov. 28, about lobbying for men's causes, misidentified the group in which Dan Logan serves as executive director. It is Free Men.

A deep rift has divided the leading scientists at work on President Reagan's antimissile defense plan. Some of them charge that the program is being seriously threatened by exaggerated assertions, hyperbolic tests and costly public-relations razzle dazzle. Others vigorously deny that those working on the huge research project have any interest whatsoever in showmanship or hyperbole. Critics outside the Government have long said the antimissile defense program, which is popularly known as ''Star Wars,'' is structured to promote the illusion of quick technical gains, no matter how great or small its actual accomplishments. But the new criticism is notable because it comes from prominent scientists who are at the forefront of the President's program. They say their technical credibility is at stake.

''If you move up missiles to a point which, it is true, is located inside Syria, but whose range of kill-sphere covers Lebanon, that affects our freedom of flight in Lebanon to a significant degree.'' - Lieut. Gen. Moshe Levy, Israel's Chief of Staff. [A1:3.]

A taxi medallion has been sold for $100,000, a record for the price of these taxi licenses, which once cost $10. The number of medallions has been frozen since 1937 so by law there are only 11,787 medallions, which license cabs to pick up street hails, in the city. But demand has been rising rapidly and so has the price. Three months ago, for instance, taxi medallions sold for $75,000 to $80,000.

The phone rings. The smooth voice on the other end addresses you by your first name and asks, ''Are you interested in the best investment in the world?'' The sales pitch has begun. The caller is touting silver or another precious metal that he predicts will soon rise in price, producing a killing for those lucky investors who can establish big positions with a small down payment. The trouble is, however, that they rarely do make a killing - or even hold onto their initial stake. The scene, described by Dennis M. O'Keefe, an enforcement official at the Commodity Futures Trading Commission, is part of what Federal courts have established as a growing fraud on the American public.