# PSYC 3250 Lecture Notes - Lecture 1: Observational Error, Extraversion And Introversion, Reliability Engineering

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Jackson scale – started with a lot and narrowed it down.

Example of conceptual reliability

Got obtained score and their true score

Can never truly know the true score – but we found out anyway

What is the reliability of the test?

Reliability is the proportion of the variance in observed scores as accounted for by true scores.

We have the variance of the obtained scores, and we have the variance of the true score.

True score/divided by the obtained score

Of the observed variable (differences we see among people) .52% of those are due to real differences

between them and 48% is due to random error

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Next problem

Gave the observed score and the error score

Use the second version of the equation, but have to figure out the true score.

Add extra column and calculate the true score

Obtained score – error score = true score

(unless it’s an opposite)

Now that we have the true scores – we do the same thing as before. True score divided by the obtained

score

Reliability

The highest reliability can be 1

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