The number of times a value appears in a sample.

The 50th percentile, often used as a measure of central tendency.

A group we are interested in studying. Often refers to a group of people, but the term is used for other subjects,

too.

Values collected and recorded with little or no checking,

calculation or interpretation.

The part of a distribution at the high and low extremes

Evidence, often personal, that is collected casually rather than by a well-designed study.

A model of a system based on the assumption that

an apparent effect is due to chance.

A distribution in which all values have the

same frequency

The derivative of a continuous CDF, a function that maps a value to its probability density.

An effect that is

unlikely to occur by chance