Scatter plot

A scatter plot draws one dot per case, with one variable on each axis, to show whether two numbers move together: when one goes up, does the other go up, go down, or do nothing?

Select any words here to ask your Maestro about them.

The cloud rises: weeks with more ads sold more. Did the ads make the sales go up?

Each dot is one week at one of the stores: what it spent on ads and what it sold. Example data.

What it's for: seeing whether two numeric variables are related, and how: whether they rise together, whether one falls as the other rises, whether the pattern is a line or a curve, and which cases break it.

To read one: each dot is one case (a store, a week, a person); how far right it sits is one variable and how high, the other. A cloud rising from left to right is a positive relationship; one falling, negative; a blob with no direction, none. A dot far from the cloud is an outlier worth a look.

What it won't tell you is the cause. Two numbers can rise together because a third one drives both, as in the figure. Before you conclude anything, split by group (area, month, customer type) and see whether the relationship holds.

You practice it in When to use a scatter plot.

How it's used

Price against units · 30 products

The cloud falls: the higher the price, the fewer units, a negative relationship. The dot that breaks the pattern, a pricey product selling like a cheap one, is the first one to check: a data-entry error, a promotion or one big customer.

When to look closer

How many dots are there?

This chart shows 13 dots. How many responses do you think are behind it?

Ask your Maestro about Scatter plot

It answers from the free course page closest to this word, the way it answers while you study.

Example

You: What does "Scatter plot" mean, in plain words?

Your Maestro: I'll explain it with a case of yours: it sticks better than a definition. Which two numbers from your work would you like to plot against each other?

Asking about: Answers from the page "When to use a scatter plot?"

Only this browser keeps what you ask here. How it works

Learn more

Scatter plot on Wikipedia

Histogram
A histogram shows how the values in a column of numbers are spread out: it cuts them into ranges of equal width and draws one bar per range, as tall as the number of values that fall in it.
Outlier
An outlier is a value that sits far from the rest, like a $9,800 order among $300 ones. It can be a data-entry error or a real, important case: before you drop it, find out which.
Log scale
A log scale is an axis where each equal step multiplies the value instead of adding to it, so 1,000, 10,000 and 100,000 sit evenly spaced.

The whole glossary