Exam 1

1. Metainformation

   Tag	Value
   file	Reliability_eur-reliability-207-en_eur-reliability-207-en
   name	eur-reliability-207-en
   section	Reliability/Analysis/Cronbach's alpha
   type	schoice
   solution	FALSE, TRUE, FALSE, FALSE
   Type	Conceptual
   Program
   Language	English
   Level	Statistical Reasoning

   Question

   Previous studies on the WISC have shown that it has a reliability of .71 (Cronbach’s alpha). A researcher working for CITO (Dutch central institute for test development) wants to know the correlation between the WISC and one of the CITO tests. He draws a sample of 102 children and finds that the correlation is .86. How is it possible that this correlation is higher than the square root of the WISC’s reliability?

   
   
   1. FALSE: Because Cronbach’s alpha gives an overestimation of the reliability in the population.
   2. TRUE: Because of sample fluctuation when Cronbach’s alpha is estimated.
   3. FALSE: Because the CITO test has a high reliability.
   4. FALSE: Because the variance in true scores on the CITO test is high.
   
   

   Solution

   • Cronbach’s alpha gives an underestimation of the reliability in the population, not an overestimation.
   • When you calculate the maximum correlation you assume that the reliability of the other variable is 1, so the high reliability of the CITO test is not the correct answer.
   • The variance in true scores on the CITO test being high is not the correct answer, because this would increase the reliability of the Cito test.

   This leaves us with the answer regarding sample fluctuation being the only correct answer, because you may have drawn an “extreme” sample from the population with a higher correlation.

   
   
   1. False
   2. True
   3. False
   4. False