Visualizing association between two measurements
A scatter plot displays individual data points on a 2D grid where the horizontal axis represents one variable and the vertical axis represents another. Each dot's position reveals the simultaneous value of both measurements for a single observation. This simple format makes patterns in association immediately visible.
Reading directions and strength of relationships
When dots trend upward left-to-right, the variables have a positive correlation: as one increases, the other tends to increase. A downward trend shows negative correlation. Tight clustering around an imaginary line indicates a strong relationship; scattered points suggest a weak one. Scattered data doesn't mean one variable is useless for predicting the other, merely that other factors also influence the outcome.
Spotting outliers and subgroups
Outliers appear as isolated dots distant from the main cloud, signaling unusual observations or potential data errors. A scatter plot also reveals subgroups: you might see two distinct clusters indicating your sample contains two populations with different characteristics. Such visual insights prompt further investigation that summary statistics alone would miss.