What is the least reliable method for selecting participants in a research study?

Convenience sampling is considered the least reliable method for selecting participants in a research study due to its inherent biases and lack of representativeness. This technique involves selecting participants based on their availability and ease of access rather than through a random or systematic approach. As a result, the sample may not accurately reflect the larger population, leading to skewed results and conclusions that may not be generalizable.

In contrast, methods such as random sampling and systematic sampling are designed to enhance reliability by ensuring that every member of the population has a chance of being selected, thus reducing bias. Probability sampling encompasses these techniques and builds a framework for achieving high levels of reliability by relying on randomization. These methods allow researchers to obtain a more representative sample, leading to more valid and reliable results in their studies.