For the record, it might be helpful to clarify several conclusions reported by Spencer Rich {"Public Beliefs on Welfare Challenged," Feb. 1}. These revolve around concerns raised by Sen. Daniel Patrick Moynihan about the drop in the real value of Aid to Families with Dependent Children benefits since 1970.

First, it should be pointed out that the article failed to distinguish between cash and noncash benefits. This is crucial because during the period when cash benefits declined, noncash benefits increased. For example, in 1960 cash benefits made up 96 percent of assistance; by 1986, only 34 percent of the welfare package came in the form of cash, while the majority portion was in the form of food, housing, health care, education, employment and other services. With noncash benefits included, federal assistance programs have grown 466 percent in real terms since 1960. It should also be pointed out that these figures also exclude state programs.

Second, the most dramatic drop in the value of cash benefits, such as AFDC, took place during the Carter years, when inflation was at a very high rate. Cash assistance has not experienced the same dramatic drop during the Reagan years, and the noncash side of the welfare package has, in fact, achieved some growth.

Finally, the article oversimplified the welfare debate by quoting a recent study arguing that "amounts of AFDC payments have no measurable impact on births to unmarried women." This assertion fails to take into account the enormous growth in the noncash side of the welfare package. Also, it assumes a direct and proportional relationship between the amount of cash assistance and the number of births. If the amount of cash on hand were the only impetus for having children, then we would see extraordinary and proportional differences in family size and birth rates between low-income and high-income families. A better question might be: "At what level of welfare security do worries about providing for children diminish?"

And last, some of these studies have failed to take into account the cost-of-living differences around the country. WILLIAM SMITH Research Director Republican Research Committee U.S. House of Representatives Washington