Population definition[ edit ] Successful statistical practice is based on focused problem definition.
However, there are obviously times when one sampling method is preferred over the other. The following explanations add some clarification about when to use which method.
Stratified sampling would be preferred over cluster sampling, particularly if the questions of interest are affected by time zone.
For example the percentage of people watching a live sporting event on television might be highly affected by the time zone they are in. Cluster sampling really works best when there are a reasonable number of clusters relative to the entire population.
In this case, selecting 2 clusters from 4 possible clusters really does not provide much advantage over simple random sampling. Either stratified sampling or cluster sampling could be used. It would depend on what questions are being asked. For instance, consider the question "Do you agree or disagree that you receive adequate attention from the team of doctors at the Sports Medicine Clinic when injured?
In contrast, if the question of interest is "Do you agree or disagree that weather affects your performance during an athletic event? Consequently, stratified sampling would be preferred. Cluster sampling would probably be better than stratified sampling if each individual elementary school appropriately represents the entire population as in aschool district where students from throughout the district can attend any school.
Stratified sampling could be used if the elementary schools had very different locations and served only their local neighborhood i. Again, the questions of interest would affect which sampling method should be used.
The most common method of carrying out a poll today is using Random Digit Dialing in which a machine random dials phone numbers. Some polls go even farther and have a machine conduct the interview itself rather than just dialing the number! Since the people who have landline phone service tend to be older than people who have cell phone service only, another potential source of bias is introduced.
National polling organizations that use random digit dialing in conducting interviewer based polls are very careful to match the number of landline versus cell phones to the population they are trying to survey. Non-probability Sampling The following sampling methods that are listed in your text are types of non-probability sampling that should be avoided: In your textbook, the two types of non-probability samples listed above are called "sampling disasters.
The article provides great insight into how major polls are conducted. When you are finished reading this article you may want to go to the Gallup Poll Web site, https: It is important to be mindful of margin or error as discussed in this article.
We all need to remember that public opinion on a given topic cannot be appropriately measured with one question that is only asked on one poll. Such results only provide a snapshot at that moment under certain conditions. The concept of repeating procedures over different conditions and times leads to more valuable and durable results.In statistics, quality assurance, and survey methodology, sampling is the selection of a subset (a statistical sample) of individuals from within a statistical population to estimate characteristics of the whole population.
Statisticians attempt for the samples to represent the population in question. Two advantages of sampling are lower cost and faster data collection than measuring the. Observational research is a group of different research methods where researchers try to observe a phenomenon without interfering too much.
Observational research methods, such as the case study, are probably the furthest removed from the established scientific method.
Before sampling, the population is divided into characteristics of importance for the research. For example, by gender, social class, education level, religion, etc.
Then the population is randomly sampled within each category or stratum. Sampling and types of sampling methods commonly used in quantitative research are discussed in the following module.
Quantitative Research Design: Sampling and Measurement - The link below defines sampling and discusses types of probability and nonprobability sampling. It consist sample definition, purpose of sampling, stages in the selection of a sample, types of sampling in quantitative researches, types of sampling in qualitative researches, and ethical Considerations in Data Collection.
Types of Sampling Methods and Techniques in Research The main goal of any marketing or statistical research is to provide quality results that are a reliable basis for decision-making.
That is why the different types of sampling methods and techniques have a crucial role in research methodology and statistics.