# Probability Samples and Validity of Generalizations

#### Introduction

Various sampling designs are available to suit different research and purposes populations. For example, although simple random sampling is logically the most fundamental probability sampling technique, it is not often in practice. Systematic sampling employs a sampling frame for selection of units that appear at a certain specified interval. This research method is, however, the functional equivalent to the simple random sampling method. The stratification method is valuable because it improves how representative a sample is by reducing the sampling error. When selecting adequate numbers of certain types of subjects who are relatively rare in the population being studied, disproportionate stratified sampling can be particularly useful. Finally, the method of multistage cluster sampling is most often utilized when there exists no list of the members of an entire population.

In Chapter 5 of Fundamentals of Research in Criminology and Criminal Justice, you learned about the three main types of probability sampling. Using your library research skills and what you have learned about sampling methods, research scholarly journal articles to find one that describes criminological research using a sample drawn from some population and respond to the following in your main post:

1. Describe the type of probability sample used in the study.
2. Draft a problem statement for a research topic relevant to criminology that could be used in conjunction with the probability sampling method you shared.
3. Differentiate the strong and weak points in how the sample was drawn in terms of how they may affect the success of the study.
4. Analyze your level of confidence in the validity of generalizations about the population based on the sample.

#### Discussion Objectives

The competencies in this discussion are supported by discussion objectives.

• Competency 2: Articulate a problem statement appropriate for examination using criminal justice research methods.
• Draft a problem statement for a research topic that could be used in conjunction with probability sampling.
• Competency 4: Use a common research method of criminal justice practitioners to examine the problem statement.
• Describe the type of probability sampling methods used in criminological and criminal justice research.
• Differentiate the strong and weak points in how samples are drawn in terms of how they may affect the success of a study.
• Analyze your level of confidence in the validity of generalizations about a population based on a sample.
• NOTE THIS IS JUST A DISCUSSION AND IS NEED OF ONE REFERENE ONLY