Reliability

Rxx is defined by the correlation between what?

• A test and a sample

• Sample and population

• True scores and measurement errors

• Test and itself

What does reliability looks at?

• Ability to reproduce results

• Ability to reproduce conditions

• Ability of accurately capturing the construct

• Ability to capture the results

Which statements more accurately apply to the following equation:

𝜎𝑋 2 = 𝜎𝑇 ^2 + 𝜎E ^2

• 𝜎𝑇 ^2 represents the measurement error

• 𝜎E^2 represents the observed score

• The total variance of scores is dived into observed score and measurement errors

• 𝜎𝑋 2 represents total variance and measurement errors

• All of the above

Which statements more accurately apply to the following equation:

𝜎𝑋 2 = 𝜎𝑇 ^2 + 𝜎E ^2

Ot^2 is the true score of what we are trying to measure.

• True

• False

Answer explanation

False, bcs it isn't what we are trying to measure (construct of interest) but what we are truly measuring.

Reliability is best defined by a formula, what is that formula?

Answer explanation

Ox^2=Ot^2+Oe^2

Where the Ox is the observed score variance that is made of true score variance and measurement error. It establishes that the scores we obtained hence is made of true variance and measurement error that interferes with our true score.

Reliability is then defined by:

Reliability (rxx)= Ot^/Ox^2. That is the proportion of true score in the observed score.

Measurement is defined by 1-Rxxx= OE^2/OX. It is the percentage of error

Which statement best describes reliability?

• Looks at the differences in individuals scores

• Looks at the replicability of results

• True score is what I am trying to measure

• True score is what I am actually measuring

• All of the above

How is reliability measured?

• Using variance

• Using reliability

• Using coefficient

• Using covariance

Is a negative coefficient possible as a rxx? (explain why or why not)

Bob calculated the reliability correlation of his test (rxx= -0.5). He asks you for help as his friend regarding his results. What should you tell him?

Answer explanation

That the correlation of -0.5 is not possible because in a reliability correlation the results vary between 0 and 1 because it is a test between itself (how much of the total variance be attributed to the true score)