* Validity refers to whether the operational definition actually measures the construct it's intended to measure. For example, if you want to measure "intelligence" and use "number of correct answers on a vocabulary test" as your operational definition, the definition could be valid if vocabulary skills are a good indicator of intelligence.
* Reliability refers to the consistency of the measurement. If the operational definition is not reliable, it means that the measurement will vary significantly even if the underlying construct is the same. For example, if your vocabulary test yields wildly different scores for the same person on different days, the operational definition is not reliable.
Here's an example:
Imagine you want to measure someone's "creativity." You define creativity as "the number of ideas generated in 5 minutes." This operational definition might be valid if the number of ideas generated is a good indicator of creativity. However, it could be unreliable if the number of ideas generated varies greatly across different occasions for the same person, perhaps depending on their mood, environment, or the specific task at hand.
In short:
* A valid operational definition accurately captures the intended construct.
* A reliable operational definition produces consistent results.
It's possible to have a definition that accurately captures a construct (validity) but yields inconsistent results (unreliability).
Importance of Both Validity and Reliability
It's crucial to strive for both validity and reliability in operational definitions. If a definition is not reliable, it becomes difficult to draw meaningful conclusions about the construct, even if it is valid.