Final answer:
To test the effect of an intervention on blood glucose outcomes in diabetes, a nurse would select an experimental study design, which provides a controlled environment to establish a cause-and-effect relationship.
Step-by-step explanation:
When planning to test the effect of an intervention to improve blood glucose outcomes in diabetes, the nurse would select an experimental study design. This type of study involves the testing of a hypothesis under controlled conditions to determine the cause and effect relationships. In an experimental study, such as a randomized controlled trial, participants are allocated into two or more groups, where one group receives the intervention (treatment group) and another serves as a control (receiving a placebo or standard care). The outcomes between the groups can then be compared to assess the effectiveness of the intervention. Other designs mentioned, such as grounded theory, ethnographic, and non-experimental, would not be suitable for this purpose as they lack the controlled environment necessary for establishing a clear cause-and-effect relationship.