ABSTRACT
This book is about the principles of psychological assessment to help researchers and clinicians better develop, evaluate, administer, score, integrate, and interpret psychological assessments. The assessments one uses should be supported by science. The book provides analysis scripts in the free software, R. Many R functions in this book are available from the petersenlab package.
Assessment is the gathering of information to improve decision making. Many assessment approaches can be used to assess people's thoughts, emotions, and behaviors, including self-report questionnaires, questionnaires reported by others, interviews, observations, biopsychological assessments, performance-based assessments, archival approaches, and combinations of these. However, there has been a proliferation of pseudoscience in assessment, including harmful and inaccurate assessments, an ethical problem. It is important to understand the characteristics of science that distinguish it from pseudoscience.
Many domains of science have struggled with a replication crisis—many findings fail to replicate. Much of the current discussion in psychology surrounding the replication crisis deals with questionable research practices. However, the field has paid insufficient attention to how lousy/noisy measures might contribute to the replication crisis. It is crucial to use assessments with strong psychometric properties, including reliability and validity, and to develop better assessments.
