With the results of a forthcoming federal study of educational software still under wraps, questions are arising about how it has been conducted--particularly the government's decision not to disclose individual performance results for the 15 computerized curriculum packages being studied. The companies involved will receive results for their own products, the public will see only aggregated findings for the four categories of programs examined in the $10 million study. Those categories are 1st grade early reading, 4th grade reading comprehension, 6th grade pre-algebra, and 9th grade algebra. Federal officials say the combined results will give valuable information about the impact of different types of curriculum packages, some of which blend computer-based exercises with textbooks and other activities. Some researchers and educators say the aggregation of the results for the different products was a lost opportunity to produce useful information on which products to buy or to avoid.