The Congressional Budget Office says the federal government spends more money per capita, on the average, in economically well-developed counties with higher personal incomes than it does in poorly developed counties where personal incomes are lower.

In the first study to analyze federal spending by counties, the CBO warns against making too much of those average patterns. They are "weak," the study say, and there are many counties, particularly in the South and the West, where the opposite is true.

On the whole, the study says, the patterns indicate it would be hard to come up with a set of federal spending policies that could be aimed reliably at such goals as promoting a healthy level of local economic development.

The study used 1975 figures to analyze spending patterns according to two standards: personal income and county rates of economic growth.

It found, among other things, the counties rarely have both low economic growth rates and low average per-capita personal income.

Only 1 per cent of all counties were both poor and declining, "it says. "Most of these were in the Southwest and South. Two per cent of all counties, most in the West, had high incomes and high growth rates."

That means, CBO said, that counties that are better off on the personal income scale and may not appar to need as much federal money tend to be worse off on the growth rate scale, and by that standard may appear to need more federal money.

Eighty-one per cent of low-income counties were in the South and the Southwest, the study found. Counties with low economic growth rates were more evenly distributed around the country, it said, but almost 75 per cent of the residents of such counties lived in the North.

The South-s major problem was low income, the study said, with more than a third of Southern counties falling near the bottom of the national income distribution scale. Even so, one-third of the South's population is concentrated in counties with relatively high incomes.

The North had a "high" proportion of low-growth-rate counties, the study said. Almost 20 per cent of all Northern counties were declining, while only 1 per cent were growing. And more than half the North's population lived in low growth counties.

In the West, patterns were much more diverse, with roughly 20 per cent of the counties experiencing rapid growth and one-third of the population concentrated in the 9 per cent of its counties that were declining.

Federal spending patterns were different in different regions, the study said. In the North, the South and the Plains states, the government spent more development money per capita in high-income counties than it did in low-income ones.

That pattern was reversed in the West, while in the Southwest there was "no consisteat spending pattern . . ." according to the study.

When growth rates are used as indicators, the study found that, on a national average, low-growth counties received $1,665 per capita in federal funds compared with $1,259 for high-growth counties.

That pattern held true in all regions. In the South particularly, low-growth counties were "major sites for federal spending," the study says.

The CBU study includes a table showing that nationally, low-growth counties averaged $1,665 per person in federal funds, high-growth counties $1,259, low-income counties $1,059, and high-income counties $1,665.