Statistics is a science dealing with the collection, analysis, interpretation, and presentation of numerical data. (Webster’s Third New International Dictionary)

 

Statistics can be subdivided into two branches: descriptive statistics and inferential statistics.

 

Population is a collection of persons, objects, or items of interest.

 

Census is data gathered from the whole population for a given measurement of interest.

 

Sample is a portion of the whole and, with statistics, if a sample is properly taken it is representative of the whole.

 

Descriptive vs. Inferential Statistics

 

If a business analyst is using data gathered on a group to describe or reach conclusions about that group, the statistics are called descriptive statistics. I.e. if one produces statistics on a subject and then uses those statistics to reach conclusions about that subject only, that is known as descriptive statistics.

 

Inferential Statistics is when a researcher gathers data from a sample and uses the statistics generated to reach conclusions about the population from which the sample was taken. I.e. the data gathered are used to infer something about a larger group.

 

A parameter is a descriptive measure of the population. It is a measurement on a population that characterizes one of its features. An example of a parameter is the mode. The mode is the value in the population that occurs most frequently. Other examples of parameters are a population's mean (or average) and its variance.[1]

 

 

Parameters are denoted by Greek letters. Examples include:

 

µ	population mean	mu
σ2	population variance	sigma square
σ	population standard deviation	sigma