INSTRUMENT
It is not possible for an instrument to be 100% unreliable and also be 100% valid. Reliability and validity are two distinct concepts that are often used to evaluate the quality of an instrument or measure.
Reliability refers to the consistency of an instrument, or how well it measures the same thing every time it is used. If an instrument is 100% unreliable, it means that it produces different results each time it is used, and therefore cannot be used to produce consistent and comparable data.
Validity, on the other hand, refers to the accuracy of an instrument, or how well it measures what it is supposed to measure. An instrument can be valid if it measures what it is supposed to measure even if it does not measure consistently every time.
Therefore, if an instrument is 100% unreliable, it is not possible for it to also be 100% valid. An instrument that is consistently inconsistent, is not measuring what it is supposed to measure and thus, it cannot be considered valid.
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