Random sampling in research methodology

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Random sampling in research methodology

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.

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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?

Random sampling in research methodology

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!

Such "robo call polls" can be very biased because they have extremely low response rates most people don't like speaking to a machine and because federal law prevents such calls to cell phones. 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. Within this section of the Gallup article, there is also an error: In 5 of those surveys, the confidence interval would not contain the population percent.A sampling frame is the first requirement in order to implement simple random sampling.

The selection of respondents or items from the frame can then be accomplished using the instruction provide with most tables of random numbers. Stratified sampling is a probability sampling method and a form of random sampling in which the population is divided into two or more groups (strata) according to one or more common attributes.

Data Preparation and Analysis - Research Methodology Course

Stratified random sampling intends to guarantee that the sample represents specific sub-groups or strata. Module 5: Data Preparation and Analysis Preparing Data.

After data collection, the researcher must prepare the data to be analyzed. Organizing the data correctly . SurveyMonkey’s polling methodology. Our SurveyMonkey research team runs surveys every day on politics, sports, current events, the media, and whatever else piques our curiosity.

Quadrats are most often used for sampling, but are not the only type of sampling units. It depends what you are sampling. If you are sampling aquatic microorganisms or studying water chemistry, then you will most likely collect water samples in standard sized bottles or containers.

Disadvantages of Simple Random Sampling One of the most obvious limitations of simple random sampling method is its need of a complete list of all the members of the population.

Please keep in mind that the list of the population must be complete and up-to-date.

Methods | Pew Research Center