Abstract
Comparison of three alternative methods for the analysis of interrupted time-series. This paper examines three procedures for analyzing interrupted time-series designs. Particularly, the functioning of correctly identified model, the general transformation approach, and an alternative approach proposed by Escudero and Vallejo (1999). Simulated data were used for investigating the effects that two inter vention models had on the estimation of parameters, error rates and power r ates of 20 ARIMA processes. The results indicate that, under manipulated conditions: 1) the accuracy of estimates is essentially the same for all three approaches. 2) The alternative approach controls the Type I error rate when α=0.05 and the model has more than one parameter; under the remaining conditions the model provides conservative rates of error. Finally, with an immediate and constant intervention effect the alternative approach is less powerful than the rest of the approaches; however, with an gradual and permanent intervention effect all three analyses provided equivalent results.
