Statistics and Probability

Frequency

How often something happens (usually during a period of time).

Estimate

To find a value that is close enough to the right answer, usually with some thought or calculation involved.

Skew

A tendency for some data values to be pulled in one direction, with a long tail.

Right-skew

Data where the tail is to the right of the graph (towards the positive x-values). Also called positively skewed.

Left-skew

Data where the tail is to the left of the graph (towards the negative x-values). Also called negatively skewed.

Symmetric

When the values of variables appear at regular frequencies and often the mean, median and mode all occur at the same point.

Outlier

A value that lies outside (is much smaller or larger than) most of the other values in a set of data.

Linear (scatter)

In bivariate data when the scatter looks like a straight line.

Non-linear

In bivariate data when the scatter forms a curve (not a line).

Histogram

A graph where the data (generally continuous) is grouped into ranges and then plotted as bars that touch each other.

Cluster

A group of values that are gathered around a particular value.

Unimodal

A set of data with a single mode.

Bimodal

A set of data with two modes.

Multimodal

A set of data with more than 2 modes.

Random (sample)

The sampling method in which each item in the population has an equal chance of being selected for the sample.

Variation

The variation that occurs randomly in the process of data collection, mainly due to chance events or human factors.