When Thursday Night Football is over, Big Bang and Life in Pieces will be followed by Mom and new comedy Angel From Hell and Elementary. Person of Interest, which did not get a full 22-episode order, will be held for midseason, as are 2 Broke Girls, Mike and Molly and The Odd Couple.
In statistics there are two kinds of means: population mean and sample mean. A population mean is the true mean of the entire population of the data set while a sample mean is the mean of a small sample of the population.
For example, the sample mean is an estimator of a population mean. If the sample mean of a particular sample 75 then the value 75 is the estimate for the population mean. Just as there are multiple possible sample statistics, there are are many possible estimators.