Singleton and Straits, 2005, Experimentation (Chapter 6)

Singleton and Straits’ (2005) chapter, “Experimentation” in the fourth edition of their book, Approaches to Social Research is an introduction to the use of experiments as a method of data collection in the social sciences.  The chapters helps readers to understand: 1) the basic logic behind experimentation, 2) stages of implementation and, 3) potential sources of error. The authors illustrate many of the ideas with reference to real-life experiments and examples.

One of the main reasons that social science researchers would engage with experimental design for gathering data is that it has long been viewed as “the optimal way to test causal hypotheses” (Singleton & Straits, 2005, pg. 155). Recalling that causal inference requires the three basic criteria of association, direction of influence (XàY), and the elimination of rival explanations (Singleton & Straits, 2005, pg. 156), experiments allow researchers to manipulate variables, control for rival explanations and observe potential associations more effectively than any other research design. Applying what Singleton and Straits (2005) refer to as the “basic requirements of a true experiment” (p. 159)*, researchers can produce results with generally high levels of internal validity and the promise of potentially high levels of external validity (best verified through experimental replication).

Singleton and Straits outline the main steps of carrying out an experiment** and discuss the importance of pretesting and creating a sense of realism despite the fact that experiments are generally performed in controlled environments. They then move on to discuss potential sources of bias/error that can emanate from both research subjects and the researchers themselves. The focus is on sources of error that are particular to experimental design such as a subjects’ willingness to “perform” and/or “look good” and therefore not react to a stimulus in a “natural” way. In two brief sections, the authors then discuss the use of experimentation in less-controlled, non-laboratory settings including field experiments (pgs. 178-181) and experimental survey research (pgs. 181-183).

While this chapter provides a useful and comprehensive introduction to experimental design in laboratory settings, this is not a setting where most social work-related research is likely to take place. One of the major disadvantages of this chapter is that by placing emphasis on laboratory experiments, that one would be more likely to find in psychology/behavioural sciences, researchers in disciplines where this type of research is less likely to be appropriate or practical, are offered significantly less guidance. Since experimental design in social work is more likely to be found when testing the impact of a psycho-social intervention seeking the cause of a particular social problem, it would have been useful for the authors to have drawn on examples of experiments that more closely align with these types of research endeavors. Examples of research studies with dependent variables relating more to human welfare than to human behaviour, would have been very useful. A discussion of more longitudinal experimental research design would also have been of value. While one can draw some parallels between lessons described in this chapter, and some experimental research in social work, discussion of research design within a natural experimental setting, such as the one reported on by Costello (2003), is nowhere to be found.  These content gaps, thus make it difficult to imagine that this chapter would be excessively informative for social work experimental research design. It is however quite useful as an introduction to key concepts in laboratory experimental design, which does help social work researchers to better understand the results of these types of studies while possibly informing our own designs.

*According to the authors, these criteria include: random assignment, manipulation of the independent variable, measurement of the dependent variable, at least one comparison or control group and constancy of conditions across groups (p. 159).

** The major steps include: “subject recruitment and acquisition of informed consent…introduction to the experiment…the experimental manipulation…manipulation checks…measurement of the dependent variable…debriefing” (pgs. 166-170).

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