Aheadline in a certain newspaper states that "most stay at first job less than 2 years." that headline is based on an online poll of 320 college graduates. among those polled, 84 % stayed at their first full-time job less than 2 years. assuming that 50% is the true percentage of graduates who stay at their first job less than two years, find the mean and standard deviation of the numbers of such graduates in randomly selected groups of 320 graduates.