A statistical human resources costing and accounting model for analysing the economic effects of an intervention at a workplace. 
The study had two primary aims.  The first aim was to combine a human resources costing and accounting approach (HRCA) with a quantitative statistical approach in order to get an integrated model.  The second aim was to apply this integrated model in a quasi-experimental study in order to investigate whether preventive intervention affected sickness absence costs at the company level.  The intervention studied contained occupational organizational measures, competence development, physical and psychosocial working environmental measures and individual and rehabilitation measures on both an individual and a group basis.  The study is a quasi-experimental design with a non-randomized control group.  Both groups involved cleaning jobs at predominantly female workplaces.  The study plan involved carrying out before and after studies on both groups.  The study included only those who were at the same workplace during the whole of the study period.  In the HRCA model used here, the cost of sickness absence is the net difference between the costs, in the form of the value of the loss of production and the administrative cost, and the benefits in the form of lower labour costs.  According to the HRCA model, the intervention used counteracted a rise in sickness absence costs at the company level, giving an average net effect of 266.5 Euros per person (full-time working) during an 8-month period.  Using an analogue statistical analysis on the whole of the material, the contribution of the intervention counteracted a rise in sickness absence costs at the company level giving an average net effect of 283.2 Euros.  Using a statistical method it was possible to study the regression coefficients in sub-groups and calculate the p-values for these coefficients; in the younger group the intervention gave a calculated net contribution of 605.6 Euros with a p-value of 0.073, while the intervention net contribution in the older group had a very high p-value.  Using the statistical model it was also possible to study contributions of other variables and interactions.  This study established that the HRCA model and the integrated model produced approximately the same monetary outcomes.  The integrated model, however, allowed a deeper understanding of the various possible relationships and quantified the results with confidence intervals.