To determine which of these studies uses a population parameter, let's analyze the nature of each scenario.

A population parameter refers to a value that represents a characteristic of an entire population, as opposed to a sample statistic, which is derived from a subset of the population.

Analysis of Each Scenario:

1. Kaisa asking 84 classmates if they voted: This scenario describes a sample of 84 classmates, not the entire population of interest. The result represents a sample statistic, not a population parameter.

2. 15% of town council meeting attendees in a rural area: This scenario gives information about a subset of people attending a specific town meeting, implying that it is based on a sample rather than the entire population of rural area residents. Thus, it is also a sample statistic.

3. 351 dog owners surveyed, with 70 owning two dogs: Here, 351 dog owners represent a sample, not all dog owners in a particular region or the country. This, too, is a sample statistic.

4. A study on the percentage of births resulting in twins across the U.S.: This scenario is based on hospital records from across the country, and it provides an estimate for all births in the U.S. Therefore, this study aims to generalize its findings to the entire population of U.S. births. This percentage (3.2%) is a population parameter because it represents an estimate for all births in the country, not just a sample.

Conclusion:

The correct answer is the fourth option, as it uses a population parameter by estimating the percentage of all U.S. births that resulted in twins.

Would you like more details on this topic or have any questions?

Related Questions:

1. What is the difference between a sample statistic and a population parameter?
2. How is a population parameter estimated when data collection on the entire population is impractical?
3. In what scenarios would researchers prefer to use sample statistics over population parameters?
4. How can sampling bias affect the validity of a study's findings?
5. What are some common methods to estimate population parameters?

Tip:

When determining if a study uses a population parameter, look for language that suggests generalization to an entire population (e.g., "across the country") rather than a specific group or sample.