Cronbach's alpha is a measure of the internal consistency or reliability of a psychometric test score for a sample of examinees. It is used to assess how closely related a set of items are as a group. A Cronbach's alpha value of 0.7 or higher indicates good internal consistency among the items in the scale. The document discusses how Cronbach's alpha relates to the variance between individual test questions and the total test score variance, with higher alpha values indicating questions are effectively measuring the intended construct.

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Cronbach’s Alpha
A correlation-based statistic that measures a scale’s internal reliability
Lorenz Duremdes, Autobiography
Dec 1 · 1 min read
Cronbach’s alpha
Cronbach's alpha
In statistics ( classical test theory), Cronbach's (alpha) [1] is a
name used for tau-equivalent reliability ()[2] as…
en.wikipedia.org
Cronbach’s alpha is an indicator of correlation between questions / items
i.e. alpha reliability. It is used to measure the internal reliability of those
questions, namely whether they measure what they intend to measure.
In psychology, when questions measure what they intend to measure, we
call them psychometrically validated questions.
When we have a set of questions with high variance that produce low score
variance, Cronbach’s alpha is low. This is because each individual question

3. doesn’t tend to measure what they intend to measure, again, because of
their high variance.
When question variance is high together with high score variance,
Cronbach’s alpha is high. This, then, means that each individual question
tends to measure what has to be measured.
A high Cronbach’s alpha seems to be synonymous with “high alpha
reliability”.
Internal validity
Internal validity means “The extent to which we can draw cause-and-effect
inferences from a study”.
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