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Chapter 2 · Survey: Measurement and Scaling · Slide 75/274

Relationship between Reliability and Validity

Relationship

2.5 · Reliability and Validity Relationship

Relationship between Reliability and Validity

Hits tightly grouped, but off-center
Reliable
but not valid
Hits loosely scattered around the center
Low reliability
low validity
Hits widely scattered and off-center
Not reliable
not valid
Hits tightly grouped at the center
Reliable and valid
the goal
✓Validity implies reliability.XO = XT ⟹ XS = 0, XR = 0
✗Non-reliability implies non-validity.XR ≠ 0 ⟹ XO = XT + XR ≠ XT
✗Reliability does not imply validity.XR = 0, XS ≠ 0 ⟹ XO = XT + XS ≠ XT
Reliability is a necessary, but not sufficient condition for validity.
QUESTIONSTAR · Dr. Paul Marx 75 / 274
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