Which of the following is an example of cluster sampling? Combining all food workers from the 67 Guilford County elementary schools and randomly choosing 150 at random to interview Randomly choosing 3 food workers from each of the 67 schools and interviewing the ones choosen Randomly choosing 8 elementary schools from the 67 in Guilford county and interviewiing all food workers at each of these schools

A. find the power of the test, when the null hypothesis assumes a population mean of mu = 450, with a population standard deviation of 156, the sample size is 5 and the true mean is 638.47 with confidence intervals of 95 b. find the power of the test, when the null hypothesis assumes a population mean of mu = 644, with a population standard deviation of 174, the sample size is 3 and the true mean is 744.04 with confidence intervals of 95% c. find the power of the test, when the null hypothesis assumes a population mean of mu = 510, with a population standard deviation of 126, the sample size is 10 and the true mean is 529.44 with confidence intervals of 95