Final answer:
Research designs testing causality should include an intervention, random assignment, a control group receiving a placebo, and possibly blinding to ensure that differences in outcomes are attributable to the intervention.
Step-by-step explanation:
The nurse researcher understands that research designs that test causality should include an intervention that involves certain key components critical for the validity of the experiment. Predominantly, it must be made sure that the only difference between the control group and the treatment group is the intervention imposed by the researcher.
Firstly, it is essential to use the random assignment of subjects to different treatment groups to eliminate the effect of lurking variables. One group should receive the intervention while the other, known as the control group, receives a placebo treatment that appears identical to the intervention but does not influence the outcome. This helps ensure that any observed differences in outcomes are attributable to the intervention itself.
To further preserve the integrity of the research, blinding of both the researchers and the participants may be employed to prevent biases introduced by expectations. Ultimately, such rigorously designed experiments allow researchers to make valid causal inferences about the relationship between the intervention (independent variable) and the outcomes (dependent variable).