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# Chapter 10 ## Quasi-Experiment Quasi-experiments lack one or more of the four key properties of true experiments. These missing ingredients can be randomization, a control group, or a validity component. However, in quasi-experiments, a "comparison group" is often used instead of a control gro...

# Chapter 10 ## Quasi-Experiment Quasi-experiments lack one or more of the four key properties of true experiments. These missing ingredients can be randomization, a control group, or a validity component. However, in quasi-experiments, a "comparison group" is often used instead of a control group. This comparison group is used to evaluate the experimental group's performance outcomes. This method relies on human judgment rather than objective criteria, making the validity of cause-and-effect inferences questionable. **Example:** Administering a drug to infants whose mothers are heroin addicts, to determine if the treatment results in weight gain or loss for low birth weight infants. The study only used an experimental group (infants of heroin-addicted mothers). No control group (infants of non-heroin-addicted mothers) was included; instead, a comparison group of infants of non-heroin-addicted mothers not part of the study was employed. **Questions to consider when no control group exists:** * **a.** Is it plausible that some external factors influenced the weight gain? * **b.** Could selection bias have impacted the weight gain results? * **c.** Could maturation (natural growth or development) affect the outcome?