In order to estimate the proportion of parents in a large school district in favor of changing the start time of school from 7:30 AM to 8:30 AM, the district sends a letter home to every family. Only 324 families returned the survey, but the results indicated that 68% of the families are in favor of changing the starting time of school. Which of the following is true about the design of this survey and the estimated proportion of parents in a school district in favor of changing the start time of school from 7:30 AM to 8:30 AM?