Relaibility

Internal Consistency

Internal consistency reliabilities (Cronbach’s Alpha) were computed on samples 1 and 5 from the standardisation exercise.  The coefficients are computed over both the combined males and females for each relevant sample. The table below provides these coefficients separately for each sample and for the entire normative sample.

15FQ™ Internal Consistencies & Item Total Correlations (ITC's)

Scale Items          N=5456 N=5577
    Alpha ITC Alpha ITC Alpha ITC
Outgoing 10 0.70 0.18 0.72 0.20 0.74 0.22
Calm-stable 11 0.67 0.16 0.63 0.14 0.65 0.15
Assertive 10 0.64 0.15 0.66 0.16 0.66 0.16
Enthusiastic 12 0.73 0.19 0.76 0.20 0.76 0.21
Conscientious 11 0.72 0.19 0.65 0.15 0.67 0.16
Socially Bold 10 0.79 0.27 0.80 0.29 0.79 0.28
Intuitive 13 0.69 0.15 0.74 0.18 0.73 0.18
Suspicious 14 0.74 0.17 0.73 0.17 0.73 0.16
Conceptual 12 0.72 0.18 0.69 0.17 0.70 0.16
Restrained 12 0.65 0.14 0.64 0.14 0.65 0.14
Self-Doubting 11 0.77 0.24 0.74 0.23 0.76 0.24
Radical 10 0.73 0.21 0.71 0.21 0.72 0.21
Self-sufficient 10 0.66 0.16 0.72 0.18 0.70 0.19
Disciplined 11 0.80 0.28 0.74 0.25 0.76 0.23
Tense-Driven 10 0.66 0.17 0.68 0.18 0.67 0.17
Distortion 13 0.75 0.19 0.69 0.14 0.72 0.16

In addition, the mean 'corrected' item-total correlations for each scale are also reported for each of these samples.  These parameters index the average association between the constituent items within a scale and the scale score itself.  Each individual item-scale score coefficient is corrected for the inflation of the coefficient due to the item's inclusion in the scale score. The above table provides the number of items which make up each scale.

This table shows that all the 15FQ™ dimensions have internal consistency reliability coefficients above .64 indicating that the test dimensions have an acceptable level of reliability.  It can be seen that the reliabilities hold up quite well across the two sub groups reported above.  The reliability of these scales compares very favourably with the reliability coefficients reported in the user manuals for both the OPQ and 16PF.  As a number of authors have noted many of the 16PF factors are very unreliable with few of the alpha coefficients being greater than .7 and many in fact being lower than .5.  Similarly the majority of the scales in the OPQ Concept and Factor models have alpha coefficients of less than .6 and a number have alpha's of less than .5. 

The following table provides a comparison of the reliabilities of the 15FQ™ scales with the comparable scales of the 16PF-A, 16PF-C and 16PF-5.  The 16PF-A  sample consisted of 1785 management applicants, the form C sample of 131 undergraduates, while the 15FQ™ sample is the total standardisation sample for the 15FQ™.  As can be seen, only one 16PF-A scale (Tense) is more reliable than  its 15FQ™ counterpart.  The 16PF-A reliabilities range between 0.18 and 0.78, this compares with a range of  0.60 to 0.87 for 16PF-5 and 0.65 to 0.79 for the 15FQ™.

Comparison of 16PF-A, 16PF-C, 16PF-5 & 15FQ™

  16PF Labels  16PF-A  16PF-C 16PF-5 15FQ™ 15FQ™ Labels
A Warm .46 .38 .69 .74 Outgoing
C Calm-stable .41 .58 .73 .65 Calm-stable
E Assertive .56 .28 .68 .66 Assertive
F Happy-go-lucky .68 .32 .74 .76 Enthusiastic
G Conscientious .61 .45 .70 .67 Conscientious
H Venturesome .78 .67 .87 .79 Socially Bold
I Tender-minded .58 .46 .76 .73 Intuitive
L Sceptical .47 .35 .60 .73 Suspicious
M Imaginative .18 .38 .71 .70 Conceptual
N Calculating .20 .27 .72 .65 Restrained
O Apprehensive .53 .70 .77 .76 Self-doubting
Q1 Experimenting .34 .26 .65 .72 Radical
Q2 Self-sufficient .36 .58 .75 .70 Self-sufficient
Q3 Controlled .53 .58 .74 .76 Disciplined
Q4 Tense .73 .41 .73 .67 Tense-driven
Social Desirability   .38 .63 .72 Distortion

Stability

The next table displays temporal consistency data for the 15FQ™.  Both short-term (2 weeks),  obtained from a sample of 80 undergraduates, and long-term (4 months) from a sample of  83 volunteers.  This table demonstrates that the 15FQ™, has a high degree of temporal consistency over the periods reported.  These test-retest coefficients compare highly favourably with those reported for similar personality instruments.  The short-term SEMs are all well below 1 sten.   

Short & Long-term Test-Retest Coefficients for the 15FQ™ (N=80, N=83)

15FQ™ Scales Short-term Test-retest Long-Term Test-retest Short-term SEM Long-term SEM
Outgoing 0.85 0.80 0.77 0.89
Calm-stable 0.83 0.71 0.82 1.08

Assertive

0.84 0.78 0.80 0.94
Enthusiastic 0.85 0.88 0.77 0.69
Conscientious 0.84 0.68 0.80 1.13
Socially Bold 0.88 0.85 0.69 0.77
Intuitive 0.83 0.80 0.82 0.89
Suspicious 0.85 0.76 0.77 0.98
Conceptual 0.86 0.70 0.75 1.10
Restrained 0.84 0.87 0.80 0.72
Self-doubting 0.82 0.71 0.85 1.08
Radical 0.87 0.78 0.72 0.94
Self-sufficient 0.85 0.79 0.77 0.92
Disciplined 0.90 0.79 0.63 0.92
Tense-driven 0.80 0.78 0.89 0.94
Distortion 0.82 0.77 0.85 0.96

 

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