Exam 1

1. Metainformation

   Tag	Value
   file	Inferential_Statistics_eur-inferential_statistics-202-en_eur-inferential_statistics-202-en
   name	eur-inferential_statistics-202-en
   section	Inferential Statistics/Effect size/Cohen's d
   type	schoice
   solution	FALSE, FALSE, TRUE, FALSE
   Type	Calculate
   Program	Calculator
   Language	English
   Level	Statistical Literacy

   Question

   A researcher wants to know whether children who frequently use headphones have worse hearing than children who never use headphones. The higher the score on a hearing test, the better the hearing. The reliability of a hearing test is .81. In the table below, the means and standard deviations of the two groups are given. What would be the effect size Cohen’s d, $d_{XT}$, if the hearing test were perfectly reliable?

   Condition	Mean	SD	N
   Headphones	10	2	30
   No headphones	11.25	3	30

   
   
   1. FALSE: .405
   2. FALSE: .490
   3. TRUE: .545
   4. FALSE: .556
   
   

   Solution

   First you use: $d_{xO} = (x̄_{O1} -x̄_{O2}) \div √ ((S^2_{O1}+S^2_{O2}) \div 2)$ to calculate $d_{Xo}$.

   This makes $(11.25 - 10) \div √((9 + 4) \div 2)=1.25 \div √6.5 = (1.25 ) \div (2.5495) = 0.490$.

   Then you use: $d_{X_O} = d_{X_T} \times √R_{XX}$

   To calculate $d_{X_T}$, this makes $0.409 \div √0.81 = 0.409 \div 0.9 = 0.545$.

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