Exam 1

1. Metainformation

   Tag	Value
   file	Inferential_Statistics_eur-inferential_statistics-201-en_eur-inferential_statistics-201-en
   name	eur-inferential_statistics-201-en
   section	Inferential Statistics/Parametric Techniques/Correlations/Phi
   type	schoice
   solution	TRUE, FALSE, FALSE, FALSE
   Type	Calculate
   Program	Calculator
   Language	English
   Level	Statistical Literacy

   Question

   Calculate the inter-item correlation between item 1 and item 2:

   

   
   
   1. TRUE: -.56
   2. FALSE: .12
   3. FALSE: -.14
   4. FALSE: .23
   
   

   Solution

   So from this table we can calculate the proportion of people who gave correct answers to both questions, this is: $10 \div 100=.1$. The covariance is then: $Sxy = Pxy - Px \times Py = =0.1 - 0.48 \times 0.50= -0.14$. The product of the standard deviations of the questions is: $√Px \times (1-Px) \times Py \times (1 - Py) = √0.48 \times 0.52 \times 0.50 \times 0.50 = 0.25$. Thus, the correlation (phi coefficient) becomes: $-0.14 \div 0.25 = -0.56$

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