Another key element in the planning process is defining the target audience. The purpose of the survey might suggest different answers. Determine approximately, how many responses would be enough from which to draw conclusions without overwhelming the investigator with too many returned surveys. What is a realistic percentage of distributed surveys that will be returned? Thirty-six percent of those TIS clients who received the 1997 survey returned them. Will the survey be mailed to all clients, to specifically selected ones, or to randomly selected ones? What are the criteria for selecting a subset of the client list?