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Explain the concept of Validity and Reliability in Measurement?


Validity

The concept of validity is to find accurate information without any unnecessary things,There are many ways to assess the validity of instrument/results ,The concept of validity explains that whether the collected result is free from errors or not it also determine whether the result is 100% accurate or not so validation involves collecting and analyzing resulting data to assess the accuracy of an instrument. Validity is the extent to which an instrument measures what it is supposed to measure and performs as it is designed to perform. It is rare, if nearly impossible, that an instrument be 100% valid, so validity is generally measured in degrees. As a process,

External validity helps obtain the degree to which a sample represents the population.
Content validity refers to the appropriateness of the content of an instrument. In other words, do the measures (questions, observation logs, etc.) accurately assess what you want to know.

Reliability

Reliability checks the consistency of an instrument and explain does the instrument consistently measure what it is intended to measure, It is not possible to calculate reliability.

Reliability is directly related to the validity of the measure. There are several important principles. First, a test can be considered reliable, but not valid. Consider the SAT, used as a predictor of success in college. It is a reliable test (high scores relate to high GPA), though only a moderately valid indicator of success (due to the lack of structured environment – class attendance, parent-regulated study, and sleeping habits – each holistically related to success).

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