The Conference Board said its consumer confidence index, with 1969-70 indicating 100, was 89.9 in August, down from July’s 92.1. The business-supported group’s buying plans index rose to 102.4 from 97.7 in July, it added. It said 24% of the households labeled present business conditions as “bad,” up from 20% a month earlier. Concerning buying plans, 8.5% of the surveyed households said they would buy an automobile in the next six months, up from 7.6% in July. Home buying plans were virtually unchanged at 3.4%, and plans to buy major appliances were down to 26% from 28% in July.