In Exercises 9–20, identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster.
Cormorant Density Cormorant bird population densities were studied by using the “line transect method” with aircraft observers flying along the shoreline of Lake Huron and collecting sample data at intervals of every 20 km (based on data from Journal of Great Lakes Research).

Verified step by step guidance

1. Understand the different types of sampling methods: Random sampling involves selecting a sample in such a way that every possible sample has an equal chance of being chosen. Systematic sampling involves selecting every k-th element from a list or sequence. Convenience sampling involves selecting a sample that is easy to access. Stratified sampling involves dividing the population into subgroups and then taking a sample from each subgroup. Cluster sampling involves dividing the population into clusters and then randomly selecting entire clusters.
2. Analyze the problem statement: The problem describes a method where aircraft observers collect data at intervals of every 20 km along the shoreline.
3. Identify the sampling method: The key detail here is the collection of data at regular intervals (every 20 km). This suggests a systematic approach, as the data is collected at fixed intervals.
4. Consider why systematic sampling is used: Systematic sampling is often used when a complete list of the population is available and the population is evenly distributed, making it efficient and easy to implement.
5. Conclude the identification: Based on the regular interval of data collection, the sampling method used in this study is systematic sampling.

Key Concepts

Sampling Methods

Sampling methods are techniques used to select individuals or observations from a larger population to make inferences about that population. Common types include random sampling, where each member has an equal chance of being selected; systematic sampling, which involves selecting every nth individual; and convenience sampling, which relies on readily available subjects. Understanding these methods is crucial for determining the validity and reliability of research findings.

Line Transect Method

The line transect method is a sampling technique used in ecological studies to estimate the density and distribution of organisms. Observers travel along a predetermined line (transect) and record the presence of species at regular intervals. This method helps in minimizing bias and allows for systematic data collection, making it easier to analyze population densities over a specified area.

Interval Sampling

Interval sampling involves collecting data at regular intervals, which can help in understanding patterns over a distance or time. In the context of the question, sampling every 20 km along the shoreline allows researchers to gather data systematically, ensuring that the sample is spread out evenly across the study area. This approach can enhance the representativeness of the sample and improve the accuracy of density estimates.