Final answer:
The nurse researcher is looking for a quasi-experimental study, which explores cause and effect in partially controlled settings and is used when full experimental control is not possible or ethical.
Step-by-step explanation:
The nurse researcher is seeking a quasi-experimental study, which examines cause and effect relationships in partially controlled settings. While experimental research is very controlled and often conducted in artificial settings, a quasi-experimental design includes some but not all of the characteristics of an experimental design, usually because full control is not possible or ethical. For instance, researchers can't ethically assign people to a condition where they would be malnourished to study its effects on school performance.
Instead, a quasi-experimental study might look at children who are already experiencing malnutrition and compare their school performance to children who are not, controlling as many other variables as possible. This type of research is valuable when it is impossible, impractical, or unethical to conduct true experimental studies, and it still allows for some insights into cause and effect relationships, even though it might have less internal validity compared to a full experimental design.