Key Concepts in Statistics and Data Analysis

Population

The entire group of individuals we want information about.

Sample

A subset of individuals in the population from which we collect data.

Parameter

A number that describes some characteristic of a population.

Statistic

A number that describes some characteristic of a sample.

Variable

Any characteristic of an individual that can take different values for different individuals.

Quantitative variable

When a variable has a numerical value (ie. number of siblings, heights of trees).

Qualitative (or categorical) variable

When a variable has a word value (ie. favorite color, type of phone).

Discrete

A value is discrete if not every possible value is allowed within a given range.

Continuous

A value is continuous if it can take on every possible value within a given range.

Mean

Add up all the values and divide by number of values.

Median

Put values in numerical order, then find the middle value.