Psychometrics of the DAS24

The data collection exercises which facilitated the development of the psychometric data is described in the Carr, Moss, and Harris (2005) British Journal of Health Psychology paper.

• Internal consistency

• Reliability – test: retest

• Content validity

• Face validity

• Concurrent validity

• Convergent construct validity

• Discriminant construct validity

Reliability of the DAS24

The  of the scale (Cronbach alpha) is 0.92.

The reliability of the scale over time is indicated by the  correlation. In the clinical population, with a six month interval, r=0.82. In the general population study, with a three month interval, r=0.88. This indicates both good test-retest reliability for the scale, and also indicates the stability of appearance concerns when there is no intervention.

Validities of the DAS24

Good  had been achieved by basing the original set of items upon patients’ descriptions of living with problems of appearance (Harris, 1982) and by ensuring that all aspects of patients’ experiences were retained throughout the development of the scale. The effectiveness of this strategy has been reflected in the consistently positive feedback we have received from patients and in the high level of internal consistency of the scale.

A study on the  of the scale (Moss 1997) did not elicit any negative comments from users in a plastic surgery population.  The Flesch Reading Ease score for the DAS 24 is 78, indicating a “fairly easy” reading level.  This is the reading level of a normal nine-ten year old.  The scale has been validated on adults who are literate in English.

was determined by comparison with the criterion measure, the DAS59. A Pearson correlation of 0.88 demonstrates the excellent relationship between the two measures.

The  and discriminant construct validity of the DAS24 was assessed by Pearson correlations with other scales chosen a priori. It was hypothesised that there would be good (0.5-0.7) positive correlations with the Crown Crisp Experiential Inventory (CCEI) total, the CCEI Anxiety subscale, the CCEI depression subscale, the two factors of social anxiety measured by Watson and Friend, (Social Avoidance and Distress, and Fear of Negative Evaluation), negative affect (Measured by the Positive Affect Negative Affect Schedule, PANAS), and shame (measured by the Internalised Shame Scale). Moderate positive correlations were found.

construct validity was tested by anticipated low correlation with CCEI hysteria, and negative correlation with positive affect (measured by the PANAS). The low correlation with and the direction of the correlation with positive affect provide strong evidence of adequate disrciminant construct validity.