Year number of dropouts 1 7 2 8 3 6 4 6 5 6 6 4 7 4 8 1 9 2 10 7 11 6 12 1 13 1 14 1 15 3 16 3 17 5 18 4 19 5 20 7 the table gives 20 years of data on the number of students in a particular school who dropped out in the ninth grade. a sample is taken to include only the last 3 years of this data. with this information, calculate both the population mean and the sample mean for ninth-grade dropouts per year. the population mean is 4.35. the sample mean is 5.33. the population mean is 4.21. the sample mean is 5.33. the population mean is 5.33. the sample mean is 3.75. the population mean is 5.33. the sample mean is 4.21.