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Univariate Data

Univariate data has the prefix "uni-", meaning one. Therefore, univariate data has one variable being studied.

Right! In the question above, I am studying the travel times to get from one place to the other. This is only one variable that I am looking for.

Bivariate Data

Bivariate data has the prefix "bi-" meaning two. Therefore, bivariate data has two variables being studied.

That's right! In the question above, we want to look at how the month in which you are travelling affects the travel time. Colder months tend to have more hazardous weather conditions, which plays a factor on travel.

When to use Univariate vs. Bivariate

You should use univariate data when looking at measures of central tendency such as mean, median, mode, range, and standard deviation. If you want to make a pie chart or histogram, or another similar chart, univariate data will be your best friend!

Now, with bivariate data, we want to compare two sets of data in order to find a relationship. This data is best to use with different kinds of plots like scatter plots, line of best fit, or correlation to see the relationship between $x$ and $y$.

Univariate vs. Bivariate Data

To prepare to enter into this explanation of uni- and bivariate data, let's start out by comparing unicycles and bicycles.

Clearly, the difference between a unicycle and a bicycle is the number of wheels; unicycles have one and bicycles have two.

Similarly, the difference between univariate and bivariate data is the number of variables. Univariate data involve one variable only (like a math unicycle), while bivariate data involve two variables (like a math bicycle).

Because there's only one variable, univariate data doesn't deal with cause and effect or relationships. It's just information on one thing.

Here's an example of univariate data: $87$% of the US Congress is white.

With bivariate data, we are looking at two variables. This lets us look at the relationship or overlap between variables.

Here's an example involving bivariate data: The teachers at School X met to examine the relationship between students' reading scores and their math scores.

$\text{Univariate vs. Bivariate data}$

An easy way to remember the difference between univariate and bivariate data is by paying attention to the prefixes of each word.

Think of words that begin with the prefix "uni-" such as unicycle, uniform, unique etc. All of these words mean one of something.

Now consider words that begin with "bi-" such as bicycle, bilingual, binoculars, etc. All of these words mean two of something.

Similarly, univariate data involves one variable while bivariate data has two. Univariate data is used to provide information on one topic. Bivariate data is used to describe the relationship between two things.

The tables below show an example of each type of data.

Univariate Data on Ice Cream Sales $$\begin{array}{|c|c|} \hline \text{Month}&\text{Avg. Sales per Day}\\ \hline \text{June}&15\\ \text{July}&26\\ \text{August}&40\\ \hline \end{array}$$

Bivariate Data on Ice Cream Sales $$\begin{array}{|c|c|c|} \hline \text{Month}&\text{Avg. Sales per Day}&\text{Avg. Temperature}\\ \hline \text{June}&15&70\\ \text{July}&26&72\\ \text{August}&40&80\\ \hline \end{array}$$

The univariate data only shows the average amount of ice cream sold per day while the bivariate data compares the sales to the temperature outside.

(Video) Univariate vs. Bivariate

by Alex McEney

Alex McEney has a good video about understanding what univariate and bivariate data are and how to identify what you are given.

$\large{\text{Summary}}$

He starts by explaining the difference between the two by comparing the two prefixes uni- and bi-. Uni- means "one" so univariate data looks at one variable. Bi- means "two" so bivariate data looks at two different variables.

He then goes trough some practice problems to show how to find what kind of data is being used in different types of problems.