Question please, Mr. Gallup

America Wants to Know: The Issues & the Answers of the Eighties, compiled by Dr. George Gallup. New York: A & W Publish ers Inc., a Norback Book. 632 pp. $19 .95.

May I please have a word with you, Dr. Doris K. Campbell? You recall that the Gallup survey organization asked you one of the hundred questions that it found the American public thirsting to have answered: ''What contributes most to a happy life?'' And in the midst of your reply you said: ''It is possible one does not always realize when one is leading a happy life.''

Does this mean that happiness is like the proverbial tree falling in the forest? It makes a sound even though no one hears it? Or can anyone really be happy without knowing it?

At any rate, Dr. Campbell, your comment leaps out in a sampling of these more than 600 pages. It is an instance of how the unexpected bits catch a reader's attention in the midst of much conventional knowledge, with a sprinkling of opinions to the left and right of establishment views.

Also, whether one agrees or not with Dr. Campbell, who writes as a former professor of psychology at universities in Tennessee and the Philippines, she prompts a moment of self-examination, which not all books do these days. It might be called counting one's blessings. One looks up in wild surmise like that character in a Moliere play who suddenly discovered he had been speaking prose all his life: Come to think of it, folks, I do have a happy life.

It may say something about America that, in a land with just about everything , the Gallupers find people wondering how to define a happy life. In fact, the questions on Americans' minds are as much the point of this book as the answers from ''more than four hundred leading experts in their respective fields.'' The largest number of pages is devoted to physical and mental health, including specific diseases, birth control, hospital care, and sexual problems. Social issues, from crime to religion, come next. Government, technology, foreign affairs, and family life are among other topics.

But the economy has the leadoff spot. Here a range of antidotes to inflation, for example, is offered, with Robert Heilbroner advocating wage and price controls on one page, and William Simon proposing curbs on spending and money supply growth on the next. But the called-upon experts do not include such symbols of the right and left as Milton Friedman and John Kenneth Galbraith, nor do they include the newsy supply-siders of recent years.

Indeed, for all the hundreds of credentialed authorities supplying answers - often just one or two - a reader is left wondering how broadly representative they are. For instance, would not today's America ''want to know'' from a roster of experts that included more than 10 percent women? And is it quite credible to have only women answer the questions of how the increase in ''working women'' has affected family life and what advantages or disadvantages a woman would have as president of the US?

Individual answers sometimes falter through loose writing or editing. For instance, it is not adequate to say: ''As one critic has put it, violence is as American as cherry pie.'' The effect is quite different when the ''critic'' who said this is known to have been 1960s black-power militant H. (Rap) Brown, advocating that blacks in Washington, D.C., arm themselves.

Among views to be taken more seriously are those dispelling alarm about the future of social security, putting world food needs in perspective, offering ways to rehabilitate prisoners, tempering concern about the scale of immigration into the US, and spelling out employment opportunities for the future.

All in all, Dr. Gallup finds the public mood upbeat in comparison with the late 1970s, reflecting a belief that problems can be solved. Perhaps many Americans - even if they don't know that they're happy - do know what a social scientist answers to a question about predicting successes or setbacks. He says that statistical data may be used to make predictions about groups of people but ''never a particular person.'' Individuals are free and unpredictable. ''Personal lives are always lived as exceptions. . . .''