Name	Population Parameter	Sample Statistic
mean	μ
proportion	p
standard deviation	σ	s

You will see the symbols that represent common statistics and parameters many times during this class.
The population mean is symbolized by the Greek letter, mu which looks like the English letter u with a long tail on the front. The sample mean is symbolized by an x with a horizontal bar over the top.
The population proportion is symbolized by the English letter, p and the sample proportion is symbolized by a p with a 'hat'.
The population standard deviation is symbolized by the Greek letter, sigma while the sample standard deviation is symbolized by the English letter, s.

Pay particular attention to the distinction between the population parameter and sample statistic. Any number that describes a characteristic of a population is a parameter. Any number that describes a characteristic of a sample is a statistic.

The mean of the population (a parameter)is not the same thing as the mean of the sample (a statistic). Thus it is crucial that different symbols are used to indicate which is which.

The average age of everyone in Vermont, is the mean age of the population or simply the population mean. The average age of a group of some Vermonter's is called the mean age of the sample or simply the sample mean. It is crucial that you learn to distinguish between the population parameter and the sample statistic.