Lecture 5.4: Devising A Valid Measure Of A Construct

I. Know what the construct is (and isn't) using common sense.

This should at least give you face validity.

II. What can go wrong with a measure with good face validity?

And what can you do about it?


         Problem           Solution(s)                                             
1. Poor reliability        Reduce error due to inconsistencies in               
weakens validity.          administering the scale by standardizing how you     
                           administer the scale.  Reduce random error due to    
                           inconsistencies in scoring by eliminating the        
                           observer or simplifying/structuring the observer's   
                           task.
                                                
2. Observer bias may       Structure/simplify the observer's task, use          
poison validity.           multiple-choice items, eliminate the observer, or    
                           use the "blind technique"                            

3. Subjects can bias the                                                        
results by                                                                      
    a. following demand    Use blind techniques  make faking hard by not        
characteristics            letting them know they are being observed, not       
                           letting them know what they are supposed to be       
                           faking, making it expensive to fake, using           
                           physiological measures that may be impossible to     
                           fake.
                                                
    b. responding in the   Make faking hard by not letting them know they are   
social desirable way       being observed, not letting them know what they      
                           are supposed to be faking, making it expensive to    
                           fake, using physiological measures that may be       
                           impossible to fake.
                                  
    c. succumbing to       Change the wording of questions so that sometimes    
response sets such as      agreeing with an item means that you are in          
the acquiescence           support of a position, whereas sometimes             
"yea-saying" bias.         disagreeing means that you support that position.    
                           use disguised questions  use behavioral or           
                           physiological measures instead of verbal measures.
   
4. Intuition may be        See that your definition is consistent with theory   
inaccurate leading to      and research about the construct you wish to         
not measuring the right    measure.  Make the case that you are measuring all   
construct.                 the relevant dimensions of the construct and have    
                           enough items to adequately represent each of these   
                           dimensions: the content validity approach.Ex:    
                           Love=lust, commitment, & trust  Argue that   
                           all the items of your subscales are measuring the    
                           same construct by showing that the answers to        
                           these items are correlated: the internal             
                           consistency argument.  Make the case that your       
                           measure must be valid because it correlates with     
                           other indicators of the construct: the convergent    
                           validity approach  Show that you are not measuring   
                           the wrong construct by showing that your measure     
                           does not correlate too highly with measures of       
                           other constructs: the discriminant validity          
                           approach.                                             


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