Analyzing Baseline Phase Data

This chapter discusses the analysis of the baseline phase. The baseline serves as the comparison for information collected during subsequent phases. It allows the researcher or practitioner to determine if the target behaviors are changing in a desirable or undesirable direction. Two different types of baselines are presented, concurrent and reconstructed. In a concurrent baseline, data are collected simultaneously, while other assessment activities are being conducted. A reconstructed baseline is an attempt to approximate naturally occurring behavior based on memories or case records. Issues related to comparing phases are discussed and illustrated, including stability of the baseline, trending data, and autocorrelation (or serial dependency). Guidance is provided on how each of these can be assessed and addressed, including the transformation of highly autocorrelated data. Examples are provided throughout to illustrate each concept.