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Probability and Statistics Terms

Get down with the lingo


Likelihood or chance of the occurrence of an event.

Qualitative Data

Data that can be represented with qualities instead of numbers, like "soft" or "muscular" or "caffeinated."

Quantitative Data

Data that can be represented with numbers.

Categorical Data

Data that can be organized into mutually exclusive groups or categories.


A diagram representing data or relationship(s) between variables.

Discrete Data

A type of data for which there's only a finite number of possible values. For example, the integers are discrete because there's no integer between 1 and 2, or between 2 and 3, etc. Also, they're very good at keeping secrets.

Continuous Data

A type of data for which there's no separation between the possible values.

Univariate Data

Data with only one variable. Not to be confused with data on a unicycle.

Bivariate Data

Data that deals with relationships between two variables.

Mean (Average)

The sum of all the data points divided by the number of data points.


The middle value of a list of data points.


The data point with highest frequency.


A set of points that divide the data set into three equal parts.

Stem And Leaf Plot

A representation of data where each data point is split into a leaf and a stem. The leaf is usually the last digit, and the stem consists of the other digits.

Bar Graph

A representation of data that uses rectangular bars to show the magnitude of categorical variables. Useful in all sorts of real-life situations.


A representation of data that uses rectangular bars to show the magnitude of quantitative variables.

Pie Chart

A circular graph divided into sectors, where the area of each sector is proportional to the relative size of the quantities represented. Also incredibly useful in real life.

Box And Whisker Plot

A representation of data that displays the range and quartiles of the data set. Looks like a kitty cat when you squint and tilt your head to the left.

Interquartile Range

The difference between the third and the first quartile.


Data points that are numerically far away from the rest of the data set. The loners of the group, if you will.

Scatter Plot

A graph of points showing the relationship between two variables.

Linear Regression

Fitting a straight line to a set of data points to find the linear relationship between the dependent and independent variables.


The measure of the linear relationship between two variables. Can be positive or negative, depending on which side of the bed it woke up on.


The ratio of the probability that an event will happen to the probability that it will not happen.


A set of outcomes of an experiment.

Mutually Exclusive Event

Events A and B are mutually exclusive if the occurrence of event A implies event B cannot occur.

Independent Event

Events A and B are independent if the outcome of event A has no effect on the outcome of event B. It's grown up! It can do what it wants!


The product of all the integers from n down to 1: n! = n × (n – 1) × (n – 2) . . . × 2 × 1. The most excited of all key terms.


One of all possible rearrangements of a collection of objects where the order of the objects is super important. To arrange n objects in r ways, we use the formula .


One of all possible ways of choosing objects out of a larger group where order does not matter. Not Judge Judy's favorite math concept, that's for sure. The formula is .

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