Statistics - True score (Classical test theory)


The true score is the score the truth that we try to estimate.

(Classical test|True score) theory asserts that raw scores are influenced by:

  • bias,
  • chance error,
  • and true scores


<MATH> \href{Raw Score}{Raw\,Score} = \href{True score}{True\,Score} + \href{bias}{Bias}+Error </MATH>


  • True Score is the score in a perfect world
  • Bias is a systematic error. Example: An instrument that will always measure with the same difference. It has an effect on the entire distribution (It shift it right or left)
  • Error: is also known as Chance error, or random chance error (For example, measurement of body temperature, if someone drink a coffer before measuring its temperature)

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