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?

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.