The short Working Alliance Inventory in parent training: Factor structure and longitudinal invariance

Area of Science:

• Psychology
• Clinical Psychology
• Psychometrics

Background:

• The Working Alliance Inventory, Short (WAI-S) is a key tool for assessing therapeutic relationships.
• Longitudinal measurement invariance is crucial for validly comparing alliance scores across different time points in therapy.

Purpose of the Study:

• To examine the factor structure of the Working Alliance Inventory, Short (WAI-S).
• To investigate the longitudinal measurement invariance of the WAI-S factor loadings and thresholds.

Main Methods:

• Confirmatory factor analyses were used to assess one-, two-, and three-factor models.
• Data from 259 Norwegian parents in Parent Management Training (Oregon model) were analyzed.
• Robust weighted least squares estimation was applied for categorical indicators.

Main Results:

• The three-factor solution (goal, task, bond) demonstrated the best fit to the data.
• Satisfactory longitudinal measurement invariance for factor loadings and thresholds was observed.

Conclusions:

• The WAI-S three-factor solution exhibits acceptable psychometric properties.
• This structure supports reliable longitudinal measurement comparisons of the therapeutic alliance.