Which of the following is an example of an independent sample?

• A. Comparing the test scores of students from two different schools selected at random
• B. Recording the weights of twins to study genetic influence
• C. Surveying the same group of people at two different times
• D. Measuring the blood pressure of patients before and after taking a medication

Answer: (A)

Verified step by step guidance

1. Understand the concept of independent samples: Independent samples are groups where the observations in one group do not influence or relate to the observations in the other group. Each sample is collected separately without any pairing or matching.
2. Review each option to identify whether the samples are independent or dependent: Dependent samples involve related or paired observations, such as measurements taken from the same individuals at different times or matched pairs like twins.
3. Analyze the first option: 'Comparing the test scores of students from two different schools selected at random' involves two separate groups of students with no inherent pairing, making these samples independent.
4. Analyze the second option: 'Recording the weights of twins to study genetic influence' involves paired data because twins are naturally matched pairs, so this is a dependent sample scenario.
5. Analyze the third and fourth options: 'Surveying the same group of people at two different times' and 'Measuring the blood pressure of patients before and after taking a medication' both involve repeated measurements on the same individuals, which are dependent samples.