In a study comparing ultrasound plus exercise versus exercise alone for subacromial impingement, with two visits per week for 4 weeks, what is the independent variable?

In a study comparing ultrasound plus exercise versus exercise alone for subacromial impingement, with two visits per week for 4 weeks, what is the independent variable?

• A. Disability index score
• B. Frequency of visits
• C. Subacromial impingement
• D. Intervention

Answer: (D)

The factor being deliberately varied to observe its effect is the intervention. In this study, participants are assigned to ultrasound plus exercise or exercise alone, so the treatment type is what the researchers change to see if it changes outcomes. The two visits per week for four weeks are kept the same for both groups, so frequency of visits isn’t the variable being tested. The subacromial impingement is the condition being studied, not a manipulated factor, and the disability index score would be an outcome measured after the intervention (a dependent variable).

The factor being deliberately varied to observe its effect is the intervention. In this study, participants are assigned to ultrasound plus exercise or exercise alone, so the treatment type is what the researchers change to see if it changes outcomes. The two visits per week for four weeks are kept the same for both groups, so frequency of visits isn’t the variable being tested. The subacromial impingement is the condition being studied, not a manipulated factor, and the disability index score would be an outcome measured after the intervention (a dependent variable).