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Validity and reliability differences in measumrement

What is the difference between instrument validity and reliability? Please give examples of each.

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Validity and reliability are two terms that are used to describe measurements.

A valid result is one that is close to the actual value. For example, consider blood alcohol measurements done on people to charge drunk drivers. The goal is to find out when the concentration of alcohol is in the blood. There are 2 tests that can be done for this: a breath test and a blood test. The breath test can occasionally give results ...

Solution Summary

This solution give a complete description of the difference between validity and reliability including several examples to make it more clear. It also answers the questions: Can something be valid but not reliable? What about reliable but not valid?