3.2 Summation notation

Of the various measures, the mean and the proportion are most important. The notation used to describe these measures appears below:

X: Refers to a population mean.

x: Refers to a sample mean.

P: The proportion of elements in the population that has a particular attribute.

p: The proportion of elements in the sample that has a particular attribute.

Q: The proportion of elements in the population that does not have a specified attribute.

Note that Q = 1 - P.

q: The proportion of elements in the sample that does not have a specified attribute. Note that q = 1 - p.

Note that capital letters refer to population parameters, and lower-case letters refer to sample.