When the government issued its latest statistics on the nation's job picture Friday, the report only heightened a longstanding controversy.

The modest two-tenths per cent drop in the unemployment rate - to 6.9 per cent of the work force - was interpreted by the Carter administration as evidence that the summer slow down is ending. It also allayed some fears that the jobless rate was on the rise.

But others had different assessments: George Meany, president of the AFL-CIO, insisted the 6.9 per cent figure was minimizing the real level of hardship in the country because it didn't count persons too discouraged to look for work. A more accurate estimate, he said, would be a jobless rate of about 9.8 per cent.

Conservative Republicans asserted the situation wasn't really as bad as it seemed because the jobless rate had been exaggerated by recent changes in the makeup of the labor force. What prompted a 4 per cent jobless rate 15 years ago would yield 6 per cent now, they said.

And black leaders complained that despite the fact that the job figures showed minority employment was not worsening as had been feared in August, they still are decidedly understating the problem in the inner city, where survey-takers often find it difficult to gather statistics.

How good are the nation's unemployment figures?

That's the question a new blue-ribbon commission is going to try to answer in an 18-month study expected to get under way early year. The nine-member panel, known formally as the National Commission on Employment and Unemployment Statistics, was set up by Congress last year to delve into the problem.

The issue is an important one, not only for the Carter administration, but for state and local governments and for private citizens as well. To begin with, having valid employment and jobless figures is crucial to setting national economic and social policy. Statistics that fall short of reporting existing conditions fully can throw policymakers off track - and possibly create added problems for several years to come.

On a more visible level, however, the statistics are important becuase they have billions of dollar riding on them - for allocation of federal grants and social programs.

Julius Shiskin, the commissioner of labor statistics, estimates that federal, state and local employment figures already determine the allocation of some $16 billion in monies for federal job programs - including such major efforts as the massive public-service jobs program - the public works job program and the countercyclical revenue-sharing program.

When programs such as unemployment compensation and some government welfare payments are counted in, the figure swells almost to $30 billion. Notes Sar A. Levitan, the manpower economist who will head the new review commission: "Political fortunes are made and lost over these figures."

The need for a review of the jobless figure has been obvious for some years now. For one thing, economic conditions have changed dramatically since the employment surveys first were developed in the late 1930s (the first real house-to-house sampling of actual employment was begun in 1940, at the start of World War II).

Not only has the composition of the labor force shifted - there's a far higher proportion of women and young people in the job market these days than37 years ago - but the concepts of who should be counted as employed or unemployed have changed. Youngsters in their early teens no longer are part of the recognized work force. College students often are.

But what really has pushed Congress into commissioning a full review of the present figures is the feeling among many law makers that the statistics don't give their districts full "credit" for unemployment at the local level - a slighting that sometimes can cost a community millions of dollars in federal grants.

Northeast congressmen, in particular, have demanded that the government expand its survey-taking to compile individual unemployment figures for each county and city - a massive task that analysts caution would be expensive and time consuming. Two states, Maryland and New Jersey, even have taken the federal government to court over the issue.

The unemployment figures were reviewed in 1962 by a high-level commission headed by Robert A. Gordon, the Berkeley economist, but that survey was narrower, aimed primarily at determining whether the figures were being shaded for political reasons - a dilemma not a issue today. Although the Gordon Commission set up new safeguards for staving off political pressures on statistics- compilers, it did little to update the employment survey itself.

Levitan's panel hopes to broaden the scope substantially, examining the basic structure of the nation's employment statistics-gathering and, hopefully, ultimately making recommendations on what changes, if any, are needed and practical. Although the names of the rest of the commission members haven't been announced fomally, the list includes academics, business and labor spokesmen and state and local representative.

The group plans to begin issuing "interim" reports on specific issues as early as next April - possibly beginning with the thorny problem of state and local unemployment figures. "The whole idea is to make this as public as possible," Levitan says. "Part of our job is to educate the public about some of these issues - even if it means some controversy."

One of the first questions the panes plans to tackle is how good present date are for policymaking, and what new statistics are needed. Another is the problem of defining who is employed and unemployed. "Many of the definitions we still use no longer are applicable in today's economy," Levitan says. is a college student who works one hour a week really part of the labor force? he asks. By today's statistical-gathering rules, he is.

In a new twist, Levitan also wants to explore ways of taking household income into account in determining eligibility for government programs. Under present rules, if a man and wife each earns $20,000 a year and one of them is laid off, the jobless partner is counted as unemployed - and is eligible for government job programs. "But the household unit isn't really in dire economic straits," he says. "The statistics in this case are exaggerating the hardship."

The commission also plans to grapple with these questions:

Should the jobless figures be counting the so-called "hidden unemployed" - the 1.1 million persons who do not show up in the statistics now because they are too discouraged by refusals to continue actively looking for work? The disparty is the basis of the AFL-CIO's complaint. The labor federation contends the unemployment rate would be far higher if these persons were included.

How to coordinate the federal unemployment figures and those compiled by state and local agencies, which compute their statistics on a totally different basis? The two have edged somewhat closer together in recent years with the development of a new formula to "adjust" the state figures to the federal rate. But the incompatibility astill leads to a lot of confusion - and political bickering.

. How to classify workers and would-be-job-seekers to provide a more realistic measure of what job conditions actually are like. Today a person is counted as employed if he did any work at all for pay during the week the sample is taken - even if it's only for an hour a week. Levitan questions whether such a definition if fair in a statistic that is supposed to measure economic hardship. What about the full-time student who is looking for a part-time job?

Despite its intentions to provide a comprehensive review of employment issues, one question the commission definitely will not get into is the politically sensitive issue of what constitutes "full employment." Although the full-employment debate is one of the most controversial of all economic disputes these days.Levitan regards it as too political and "not within the commission's mandate."

Still, many analysts believe that even without resolving the full-employment issue, if the commission accomplishes its goals it will be doing the nation a valuable service. While the Bureau of Labor Statistics' Shiskin defends his jobless figures as accurate and unbiased, he concedes the time is right for a review of definitions and procedures. And the panel's report could have impact for generations to come.