Consider a random variable Y. What is the difference between the sample average and the population mean? The population mean is a true measure of the central tendency of the distribution of Y whereas the sample average is an estimator of the population mean. Both the population mean and the sample average are estimators of the central tendency of the distribution of Y. The sample average is a true measure of the central tendency of the distribution of Y whereas the population mean is an estimator of the sample average. Both the population mean and the sample average are true measures of the central tendency of the distribution of Y.