In the study depicted in the figure above, why might researchers have measured blood pressure twice?

• A. To intentionally introduce variability into the data.
• B. To compare blood pressure between two different groups of participants.
• C. To ensure that the blood pressure monitor was functioning incorrectly.
• D. To increase the reliability of the measurements by reducing random error.

Answer: (D)

Verified step by step guidance

1. Understand the concept of reliability in scientific measurements: Reliability refers to the consistency and dependability of measurements. Researchers aim to reduce random errors to ensure their data accurately reflects the true values being studied.
2. Recognize the role of repeated measurements: Taking multiple measurements of the same variable (e.g., blood pressure) helps to identify and minimize random errors that may arise due to factors like device variability or participant conditions.
3. Consider the purpose of measuring blood pressure twice: By measuring blood pressure twice, researchers can average the values or compare them to detect inconsistencies, thereby increasing the reliability of the data.
4. Eliminate incorrect options: Review the provided choices and rule out options that do not align with the goal of reducing random error. For example, introducing variability intentionally or ensuring the monitor is functioning incorrectly are not valid scientific practices.
5. Select the correct answer: Based on the reasoning above, the correct answer is 'To increase the reliability of the measurements by reducing random error.' This aligns with the scientific principle of improving data accuracy through repeated measurements.