Arlington County Board candidate Mary Margaret Whipple has called for the creation of a task force to study ways to help stabilize the county's population and keep it from becoming increasingly dominated by young singles and the elderly.

At a press conference announcing her proposal last week, Whipple, a Democrat, also accused the current Republican-backed County Board majority of neglecting day-care needs and of making School Board appointments for "personal rather than educational reasons."

Although the county's population diversity is a "very positive factor," Whipple said, "families provide stability to a community, and right now they are a decreasing proportion of Arlington's population . . . . Clearly it is time for a concentrated effort to retain Arlington's families and to attract new ones. We must let families know about our services and at the same time seek to improve them.

"We are not a community of transients and we don't want to become one," she said.

Whipple, who is running against GOP-backed independent board chairman Stephen H. Detwiler, cited 1980 U.S. Census data showing that 40 percent of Arlington's households contain only one person. She also noted that county population increases in the past decade have occurred only among those over 65 years old and those aged 25 to 34.

At the same time, she said, the average household size has decreased from 2.43 persons in 1970 to 2.07 persons in 1980 while the number of one- or two-person households has increased by 20 percent.

Her proposal calls for the County Board to appoint a task force to determine what services families need and what factors influence a family's choice of location. The task force would analyze community services and recommend improvements.

Detwiler said he sees no need for such a task force, however.

"The problem of declining family size is not unique to Arlington," Detwiler said. "There's been a large increase in the number of housing units in the county and there are people moving in every day. If Mrs. Whipple has a secret formula to make people have larger families, I wish she'd share it."

Whipple also complained that the board majority voted against fully funding the county's Child Care Office when it lost federal funds earlier this year. As a result, there was a net loss of $55,900 and three positions. The loss forced the county to stop inspecting most child-care facilities for health and safety conditions and to stop providing training in proper child-care operation, Whipple said.

Whipple, a former School Board chairman, also criticized the County Board appointments of Republicans Margaret A. Bocek, Claude M. Hilton and Simone J. (Sim) Pace to the School Board. Though they may be active in their children's schools, Whipple said, they did not have major experience with the school system before their appointments.

Pace disagreed, saying he was on the panel that set criteria for selecting a new superintendent and has been a teacher at Northern Virginia Community College for 10 years. Bocek was on the School Board's English advisory committee and graduated from a teacher's college. Hilton said he has served on several PTAs.

"I'm very disappointed she would drag the fine names and reputations of outstanding School Board members into a county campaign," Detwiler said. "Each of them is outstanding and eminently qualified."

Whipple also noted that the County Board majority cut $1 million from the fiscal 1982 school instructional budget and that the Republican-controlled School Board last year reduced remedial programs, funding for the libraries, public information and volunteer services.

The School Board also unexpectedly raised fees for the extended-day program without a public hearing, although the fees were subsequently lowered when the County Board contributed funds to offset the increase, Whipple said.