ABSTRACT
This chapter discusses the empirical obstacles in the way of determining whether a relationship is causal and focuses on how to design the study to avoid them successfully. It examines the practical decisions that researcher must make at the planning stage of their study to ensure that it will permit them to draw causal conclusions. The chapter explains what to do about multivariable causation in planning researchers' study. It describes the possibility of coming to believe mistakenly that one variable is causally influential when another variable is “really” the cause—the “hidden third factor” error, also called “spurious correlation” in sociology and social psychology. A change in demand for a product causes a change in the price, which causes a change in the supply of the product, which causes a change in the price, which causes a change in demand, on and on forever.
