Scatter Plot

A scatter plot places one dot for each observation using two numeric variables — one on the horizontal axis, one on the vertical — so you can see how the two move together. It is the single best chart for spotting a relationship: an upward cloud suggests they rise together, a downward cloud suggests one falls as the other rises, and a shapeless blob suggests no clear link.

It is also where you catch surprises a correlation number would miss: a curved bend, distinct clusters, or one outlier dragging the whole story. Remember that an upward trend shows association, not cause — two things can move together because a third hidden factor drives both, so correlation seen in a scatter plot is not proof of causation.