Statistics — Common Mistakes

A collection of the most common reasoning errors students make in statistics, with explanations of why those interpretations fail.

Statistics mistakes usually happen when a summary, graph, or probability is asked to support a claim it cannot actually support. These pages focus on the gap between the calculation and the conclusion.

Use this index when a result looks numerically correct but the interpretation still feels unstable. Repairing the concept-level mistake early usually prevents it from spreading into later topics.

Use these pages to check:

whether a graph or average is describing the data honestly,
when a sample or study design weakens the claim you want to make,
and where a changed sample space or hidden variable breaks the reasoning.

The linked guides below are most useful when a conclusion sounds persuasive but you are not sure the data justify it.

That is usually where statistics becomes less about arithmetic and more about disciplined interpretation.