Reliability and Validity

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```					  Reliability and Validity
Scale
Evaluation
Reliability                           Validity

Content
Test-Retest
Internal                 Criterion
Alternative    Consistency
Forms                                               Construct
Convergent
Validity
Discriminant
Validity   Nomological
Validity
Determination of Validity and Reliability

Constructs Tests Required

Reliability                       high

Convergent validity                   high

Discriminant validity                  low

nonsense                         low
Multitrait - Multimethod Matrix (Campbell & Fiske,
1959)

Method 1               Method 2
Trait a Trait b       Trait a Trait b
Trait a       b1
Method 1
Trait b       m1      b1
Trait a       va      d             b2
Method 2
Trait b       d       vb            m2          b2

{
b1   = reliability for method 1
Correlation        va   = convergent validity for both methods wrt trait a
coefficients       m1   = discriminant validity for method 1
d    = “nonsense”-correlation
Requirements:
• v > 0 and "high enough"
• v>d
• v>m
• d low
Example
Mosher Forced Choice Guilt Scale

3 traits
    Hostile guilt
    Guilt concerning morality
3 methods
     Incomplete sentences "When I dream about sex …"
     Forced choice
    " When I dream about sex …"
a)     I don't remember a thing in the morning
b)     I feel happy when I get up
     True/False
    "When I dream about sex I wake up feeling happy"
MTMM matrix for the Mosher Forced Choice
Guilt Scale

Sexual            TF                FC                 IS
Hostile      (true/false)     (forced choice)   (incompl. sent.)
Morality
SG    HG MC SG HG MC SG HG MC
SG   .91                           FC very reliable,
TF HG   .52   .84                      TF too, IS not
MC   .68   .50   .84                           Good
convergent
SG   .86   .56   .73   .97                    validity
FC HG   .53   .83   .53   .61   .96            Discriminant
validity OK
MC   .63   .54   .83   .70   .58   .92
SG   .78   .51   .63   .79   .54   .57 .72
IS HG   .24   .67   .23   .33   .73   .37 .32 .65
MC   .47   .40   .66   .48   .49   .70 .49 .28 .55

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