American consumers retained "a relatively high level" of confidence in the economy during February, after a substantial increase in confidence during January, a business research organization said yesterday.

The Conference Board said its Consumer Confidence Index fell slightly to 95.2 in February from 95.4 in January, when the index rose 10 points from December's level. The index, calculated after a monthly survey of 5,000 households nationwide, is based on the 1969-1970 confidence level equaling 100.

People responding to the survey also seemed to be growing more concerned about their income levels, the Conference Board said. It said fewer than 26 percent of those responding to February's survey expected their incomes to rise over the next six months, down from about 29 percent in January.

The survey, conducted for the Conference Board by NFO Research Inc. of Toledo, Ohio, also asks consumers about their plans to buy homes, cars and major appliances. It found that 8.8 percent of those surveyed said they planned to buy a car within the next six months, virtually unchanged from 8.9 percent in January.

Plans to buy a home within the next six months fell slightly to 3 percent in February from 3.2 percent in January, the Conference Board said. It said plans to buy major appliances rose to 29.3 percent in February from 27.1 percent in January.