population mean of a sample average
Sample Mean. The sample mean is the average of all the items in a sample (a group of observations). The following is the formula for the sample mean x of a set {x1, x2, ..., xn} of n observations from a given distribution: The population mean is the average of all the items in a population. Because a population is usually very large or unknown, the population mean is usually an unknown constant. An estimate of the population mean is the sample mean.
In statistics, population refers to the total set of observations that can be made. For example, if we are studying the weight of adult women, the population is the set of weights of all the women in the world. If we are studying the grade point average (GPA) of students at Harvard, the population is the set of GPA's of all the students at Harvard. AP Statistics.