The federal government wants a little information from you.

Are you married to the person you live with? Does your house have a flush toilet? How much would you sell your house for? How many babies have you had, not counting stillbirths? How well do you speak English? How much was your salary last year? How much did you receive in welfare payments?

On Aprril 1, 1980, the Census Bureau will pose those questions in households around the country as the government, for the 20th time in the nation's history, sets out to find out how many Americans there are - or, more precisely, how many people are residents (legal or illegal) of the 50 states, the District, Puerto Rico, the Virgin Islands and various trust territories in the Pacific.

But the numbers - which will be used among other things to reapportion the House of Representatives - are only one aspect of the national survey. The government also will be asking a broad range of questions about people's way of life.

The Census Bureau has just started printing 160 million copies of questionnaires that will be distributed next spring, mostly by mail, to every household.

There are two different questionaires. Most people - 78 percent of the population - will receive what the bureau calls a "short form," asking seven personal questions such as age, race, marital status, and relationship to others in the household, and 12 housing questions, including the flush toilets query and questions about the number of rooms in the home and monthly rent paid or the dollar value of the house.

The remaining 22 percent, chosen at random, will be asked all those questions, plus dozen more about their ancestry, language ability, health, divorce history, employment, income and housing.

The use of two questionnaires is the government's compromise solution to a basic census dilemma: How to make the survey broad enough to satisfy government, corporate and academic data users without making it such a pain in the neck that people refuse to answer.

Some people, judging from mail to congressmen on the subject, think the census has gone too far in the pain-in-the-neck direction.

Rep. William Lehman (D-Fla.) wonders how he can justify the survey 'to somebody who writes me a letter saying that "the census is asking me whether I have been divorced or not and I don't think it's the government's business . . .' What am I going to tell them?"

In addition to the feeling that the census is too intrusive, Lehman and others are concerned that people may find the survey, particularly the longer questionnaire, too much trouble to deal with.

The Census Bureau says that concern is unrealistic. I says the average family will be able to finish the short form of the 1980 survey in 15 minutes, and the long form in 45. In a practice run yesterday, this reporter, answering for a household of three, took 11 minutes to complete the short form and 75 minutes for the long one (including the time it took to look up last year's water bill).

Anyone who refuses to fill out a census form will be liable for prosecution under a federal misdemeanor statute that sets a $100 fine for willful failure to respond. The government has brought six cases under the law in the last 20 years. All ended in convictions, but two of those were reversed on appeal.

The 1980 census questions already reflect some of the changes in the society they will measure. Responding to the change in family roles, the census has eliminated the term "head of houshold." In questions dealing with occupation and income the pronoun "he" has been replaced by the phrase "this person."

The bureau has dropped the question asking if there is a television in the home. In 1970, 95.7 percent responded "yes" and the government thinks TV ownership is now nearly universal. The 1980 long form asks about ownership of air conditioners, heat pumps, cars, small trucks and vans.

The long form will ask each respondent's income in seven different categories of earnings, whether the respondent has had any physical or mental disability, and several questions about work experience and the respondent's current occupation.

The 1980 census also mirrors the nation's growing ethnic consciousness. When the survey was being written, numerous racial and national groups lobbied for specific identification in the questions, and the bureau responded by increasing the number of possible answers to the "race" question from nine in 1970 to 15 on the new forms.

Hispanics were the big winners here. For the first time, every American will be asked in 1980 if he or she is of Hispanic descent, and those answering "yes" will then further identifying themselves among four subcategories (Mexican, Puerto Rican, Cuban, other).