Claudia Wayne {letters, Dec. 1} states that "as the Census Bureau's 1986 wage-gap figure confirms, sex-based wage discrimination still plagues American women -- who now earn 64 cents for every dollar earned by males." But neither of the Census Bureau's recent studies of money income and poverty and of male-female wage differences confirms or supports any such claim.

Experts in the field acknowledge what comparable-worth advocates like to sweep under the rug: there is no statistical technique sophisticated enough to explain all of the nondiscriminatory reasons why persons in different jobs receive different pay. These studies always identify a portion of such a wage gap as "unexplained." The unexplained wage gap is just that -- unexplained -- and not evidence of discrimination.

While some advocates of comparable worth frequently seek to mislead others by the misuse of the unexplained portion of a pay gap, the Census Bureau's recent study of male-female work and wage differences acknowledges this elementary point. It noted that the average wage for full-time female workers was 70 percent of the average wage for full-time male workers. The study said that factors such as education and interruptions in work-force participation accounted for between 60 percent and 66 percent of this gap.

The Census Bureau carefully noted its study's limitations: "The earnings model . . . presented here is not . . . definitive. The determination of wages is a complex process that depends on factors that could not be fully captured in this model. For example, the model does not attempt to measure the effect of ability, preferences for certain types of nonmoney remuneration, or the effect of physical capital differences among industries." A Census Bureau official reiterated this cautionary note, according to press reports.

None of this is to suggest that sex discrimination in wages is nonexistent. But the simplistic invocation of a general wage gap or a gap in pay between two specific jobs as a basis for a claim of such discrimination is entirely misguided. Current laws such as the Equal Pay Act and Title VII already forbid wage discrimination and provide means of proving it without resort to what President Reagan has aptly called a "harebrained" concept such as comparable worth. MARK R. DISLER Deputy Assistant Attorney General Civil Rights Division, U.S. Department of Justice Washington