In Exercises 9–20, identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster.
Highway Strength The New York State Department of Transportation evaluated the quality of the New York State Thruway by testing core samples collected at regular intervals of 1 mile.

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 nth item 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 taking a sample from each subgroup. Cluster sampling involves dividing the population into clusters and then randomly selecting entire clusters.
2. Identify the key details in the problem: The New York State Department of Transportation is testing core samples collected at regular intervals of 1 mile.
3. Recognize the pattern of sample collection: The samples are collected at regular intervals, which suggests a systematic approach.
4. Relate the pattern to a sampling method: Since the samples are collected at regular intervals (every 1 mile), this aligns with the definition of systematic sampling.
5. Conclude the type of sampling used: Based on the regular interval collection method, the sampling method used is systematic sampling.

Key Concepts

Sampling Methods

Sampling methods are techniques used to select individuals or items from a larger population to make inferences about that population. Common types include random sampling, where every member has an equal chance of selection; systematic sampling, which involves selecting every nth member; and convenience sampling, which relies on readily available subjects.

Systematic Sampling

Systematic sampling is a method where samples are selected at regular intervals from a larger population. For example, if a researcher decides to take samples every 10th individual in a list, this approach ensures a structured and evenly distributed selection process, which can help reduce bias compared to purely random sampling.

Core Sampling

Core sampling is a technique used to obtain a cylindrical section of material from a specific location, often used in geological and construction studies. In the context of the New York State Thruway, core samples taken at regular intervals help assess the quality and strength of the highway's materials, providing critical data for infrastructure evaluation.