\section{Choosing a graphic}
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\multicolumn{1}{c}{Question} & \multicolumn{1}{c}{Interface}\\\midrule
How large is a value? & \key{\gradbar{value}}; use a negative min for signed values.\\
How do two values compare? & \key{\gradcompare{reference}{current}} for layered bars;
\key{\graddumbbell{reference}{current}} for connected points.\\
What are the bounds? & \key{\gradrange{lower}{upper}} for supplied endpoints.\\
What makes up the total? & \key{\gradstack{list}} for additive, common-unit contributions.\\
How does a series change? & \key{\gradspark{list}} for equally spaced observations.\\
What is the uncertainty? & \key{error minus} and \key{error plus} on a point estimate.\\
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