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Sampling (statistics)

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Judgment sampling guess a good-enough sample You are expert and there is no other choice. Method Best when Selective sampling gut feel Focus is needed in particular group, location, subject, etc. Theoretical sampling testing a theory Theories are emerging and focused sampling may help clarify these. Home Top Menu Quick Links. Probability methods This is the best overall group of methods to use as you can subsequently use the most powerful statistical analyses on the results.

When population groups are separated and access to all is difficult, eg. Proportionate quota sampling in proportion to population sub-groups. You know the population distribution across groups, and when normal sampling may not give enough in minority groups. Non-proportionate quota sampling minimum number from each sub-group. Modal instance sampling focus on 'typical' people. When sought 'typical' opinion may get lost in a wider study, and when you are able to identify the 'typical' group.

You are specifically seeking differences, eg. Specify a sampling method. There are basically two ways to choose a sample from a sampling frame: There are benefits to both.

Basically, if your sampling frame is approximately the same demographic makeup as your population, you probably want to randomly select your sample, perhaps by flipping a coin or drawing names out of a hat. But what if your sampling frame does not really represent your population? For example, what if the school where Brooke works has a lot more men than women and a lot more whites than minority races?

In the population of every college student in the world, there might be more of a balance, but Brooke's sampling frame her school doesn't really represent that well. In that case, she might want to non-randomly select her sample in order to get a demographic makeup that is closer to that of her population. Determine the sample size. In general, larger samples are better, but they also require more time and effort to manage.

If Brooke ends up having to go through 1, surveys, it will take her more time than if she only has to go through 10 surveys. But the results of her study will be stronger with 1, surveys, so she like all researchers has to make choices and find a balance between what will give her good data and what is practical.

Once you know your population, sampling frame, sampling method, and sample size, you can use all that information to choose your sample. As you can see, choosing a sample is a complicated process. You might be wondering why it has to be that complicated. Why bother going through all those steps? Why not just go to a class and pull some students out and have them fill out the survey?

Why is sampling so important to research? Get access risk-free for 30 days, just create an account. To answer those questions, let's look at an example of an actual study that was done in the mids.

A researcher mailed out surveys to a bunch of married women and asked them questions about their marriage. As you can imagine, this study sent shockwaves through America as husbands looked at their wives and calculated the probability of dissatisfaction or affairs. Those who got the survey, filled it out, and returned it were much more likely to be dissatisfied than those who didn't return it.

Maybe those who were happy in their marriage were too busy having fun with their spouse to cheat. That's why sampling is so important to research.

If a sample isn't chosen carefully and systematically, it might not represent the population. And if it doesn't represent the population, then the study can't be generalized to the world beyond the study. Let's go back to Brooke for a moment. She wants to know, in general, how much stress college students experience during finals.

Let's say that she decides to save some time and bypass the normal sampling method. Instead, she just sets up a table outside the mental health office on campus where students go to see counselors. As students go in or out of the office, she gives them the survey.

But in this example, Brooke's sample might end up being only college students who are seeing counselors. They might be more anxious or depressed or high-strung in general, so the stress of finals might hit them particularly hard.

As a result, Brooke's sample doesn't represent the population, and she might end up thinking that college students experience more stress than they actually do. The sample of a study is the group of subjects in the study. Sampling is the process whereby a researcher chooses his or her sample. The five steps to sampling are:. It is important for researchers to follow these steps so that their sample adequately represents their population.

If not, the results of the study could be misleading or skewed. To unlock this lesson you must be a Study. Did you know… We have over college courses that prepare you to earn credit by exam that is accepted by over 1, colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page. Not sure what college you want to attend yet? The videos on Study. Students in online learning conditions performed better than those receiving face-to-face instruction. By creating an account, you agree to Study. Explore over 4, video courses. Find a degree that fits your goals. What is Sampling in Research? In this lesson, we'll look at the procedure for drawing a sample and why it is so important to draw a sample that represents the population.

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Register to view this lesson Are you a student or a teacher? I am a student I am a teacher. What teachers are saying about Study. Are you still watching? Your next lesson will play in 10 seconds. Add to Add to Add to. Want to watch this again later? Sampling Techniques In Scientific Investigations. Selecting a Problem to Research. What is a Hypothesis?

Sampling - This resource provides a brief overview of sampling and sample size with links to descriptions of purposeful sampling strategies. A Guide to Using Qualitative Research Methodology - The file linked below contains a full description of how to conduct qualitative sampling, including a chart that lists the types of sampling techniques and includes examples. Sampling Designs in Qualitative Research - The following article discusses sampling designs and ways to make the sampling process more public.

This pin will expire , on Change. This pin never expires. Select an expiration date. About Us Contact Us. Search Community Search Community. Qualitative Sampling Methods The following module describes common methods for collecting qualitative data. Describe common types of qualitative sampling methodology. Explain the methods typically used in qualitative data collection.

Describe how sample size is determined. Purposeful Sampling is the most common sampling strategy. In this type of sampling, participants are selected or sought after based on pre-selected criteria based on the research question.

For example, the study may be attempting to collect data from lymphoma patients in a particular city or county. The sample size may be predetermined or based on theoretical saturation, which is the point at which the newly collected no longer provides additional insights.

Click on the following link for a desciption of types of purposeful sampling:


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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.

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Sampling Methods. Sampling and types of sampling methods commonly used in quantitative research are discussed in the following module. Learning Objectives: Define sampling and randomization. Explain probability and non-probability sampling and describes the different types of each.

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Probability sampling is a technique wherein the samples are gathered in a process that gives all the individuals in the population equal chance of being selected. Many consider this to be the more methodologically rigorous approach to sampling because it eliminates social biases that could shape the research sample. Simple Random Sampling (SRS) Stratified Sampling; Cluster Sampling; Systematic Sampling; Multistage Sampling (in which some of the methods above are combined in stages) Of the five methods listed above, students have the most trouble distinguishing between stratified sampling and cluster sampling.

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RESEARCH METHOD - SAMPLING 1. Sampling Techniques & Samples Types 2. Outlines Sample definition Purpose of sampling Stages in the selection of a sample Types of sampling in quantitative researches Types of sampling in qualitative researches Ethical Considerations in Data Collection. What are the main types of sampling and how is each done? Simple Random Sampling: A simple random sample (SRS) of size n is produced by a scheme which ensures that each subgroup of the population of size n has an equal probability of being chosen as the sample.. Stratified Random Sampling: Divide the population into "strata".There can be .