Analyzing Psuedo-Time Series Interventions

Abstract

A time series evaluation design of use in analyzing certain kinds of "case-flow "programs is described. Because it combines features of both conventional time-series designs and nonequivalent comparison group quasi-experiments, we refer to it as a "pseudo-time series" or PTS design. Statistically, PTS designs resemble replicated surveys that independently sample some population at successive time points. The substantive analogy is a program that services a rapidly changing clientele the members of which usually enter and exit the program on only one occasion. This article describes the distinguishing features of PTS designs, outlines a methodological strategy for analyzing PTS data, and shows how this strategy can be used to overcome design weaknesses in certain case-flow evaluation studies.