Ishikawa variance diagram
This example was created on the base of the figure from the website of the WSU College of Veterinary Medicine of the Washington State University. [vetmed.wsu.edu/courses-jmgay/images/Ishikawa%20Variance%20Diagram.jpg]
"Internal validity is a property of scientific studies which reflects the extent to which a causal conclusion based on a study is warranted. Such warrant is constituted by the extent to which a study minimizes systematic error (or 'bias')." [Internal validity. Wikipedia]
The fishbone diagram example "Ishikawa variance diagram" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Fishbone Diagrams solution from the Management area of ConceptDraw Solution Park.