Research projects

Purposive sampling – An essential part of many research projects

The Internet provides us with many research studies, which are based on purposive samples. This is because it works well for most research projects. However, it would be best to find out about this even if you are not running them yourself.

Indeed, most of the facts and results you see on the internet depend on this sampling strategy. Some studies might provide false information or mislead people based on facts. Fortunately, this article can help you understand how it works.

That’s why I’ll start by explaining what the purposive sampling technique is and why researchers tend to use it. Next, I’ll explain how people perform this method in different ways. This way, you can see how this research technique shapes the studies you find online.

Why do we use purposeful sampling?

Search the internet enough and you will find many studies that provide interesting anecdotes. Contrary to popular belief, conducting research has more important purposes.

No matter their subjects, their main goal is to learn something. You can do this by observing the particular subject or phenomenon of your choice and then writing down what you see.

This alone will not be enough as you need to organize this data. Otherwise, people would have a hard time using this data, even you. This is why researchers employ various methods.

The purposive sampling technique is the most common. Also known as subjective sampling, it involves choosing a group of people or other subjects that matches your intended study.

You choose them based on your understanding of your favorite subject. Most of the time, purposive sampling involves people. You might be wondering if this is just a lazy approach to research.

Maybe the experts just don’t want to ask more people, so they stick to a few. This is called convenience sampling, and purposive sampling has nothing to do with it.

As the name suggests, the former aims to make the search method easy for searchers. For example, they could simply choose people nearby or people they already know.

Now you might be wondering why researchers spend time choosing their respondents. Let’s take a closer look at the reasons below:

It’s not realistic to ask everyone.

Have you ever found a stat involving everyone on Earth as respondents? Even the biggest companies don’t because of the steps you’ll have to follow.

You will need to require everyone to participate in your data collection in some way. It’s utterly impossible, even for Mark Zuckerberg and Facebook.

I used this exaggerated example to emphasize that a study needs limits because people have limits too. The purposive sampling technique helps researchers observe a realistic number of people.

Read more: How research methods still help us today

Your study only applies to certain groups of people.

You don’t need to know the opinion of everyone in the world just for your study. Most often, you just need to collect feedback from a certain population.

This allows you to observe that the right people get the most accurate results possible. Additionally, focusing on a sample population helps you create a cohesive and concise study.

Your data won’t have to add too many unnecessary factors or variables. Not to mention it saves you time and money. If you need to ask for a survey in a city, you don’t have to ask all the inhabitants.

Subjective Sampling vs Probability Sampling

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Purposive sampling can look like random sampling. He chooses a relatively small group of people for a study. However, probability sampling has a huge difference.

As their name suggests, probability sampling techniques leave their selection to chance. This helps a study eliminate variables that may be biased by researchers.

This may not work in a study where respondents need to share common traits. For example, a study of blond hair may not work with probability sampling techniques because it may include people with dark hair.

On the other hand, purposive sampling is based on specific factors. For example, a study of people with blond hair might use it by focusing on a city.

It is not a matter of convenience sampling because the selection always follows the objectives of the study. It is also not probability sampling, as it follows sample selection criteria.

What are the types of purposive sampling?

We have established that researchers choose their samples based on their expertise. They have different ways of doing it. You can categorize this diverse range of methods as types of purposive sampling.

After all, there are many things you can observe in our world. It is impossible that one method allows you to observe them all. This is why researchers have developed all sorts of purposive sampling methods.

The objective is to adapt the right strategy to a particular phenomenon. Remember that there is always a margin of error in every study. Find the most suitable option, not the perfect one.

Heterogeneous or maximum variation sampling

You use this type of purposive sampling when you need to test a wide variety of cases related to a particular phenomenon. This allows you to confirm whether it will remain constant in each scenario.

For example, you can poll how many people know cryptocurrency. If you are using maximum variation sampling, you are asking all types of people in a certain area.

This way, you can uncover the subjective or generalized assumptions of a certain population about that digital asset. This type of purposive sampling eliminates the bias associated with choosing a specific age group.

Typical Case Sampling

You could compare a certain trend with the status quo. For example, you can check the effect of remote work trend on ordinary employees. You can check their perception about it or how it affected their career goals.

Typical case sampling might be the only appropriate method for this instance. You can ask regular employees research questions to get their opinion.

This ensures that your primary data sources are relevant to the topic. Note that various factors can still affect the sampling of typical cases.

Sampling of extreme or deviant cases

As the name suggests, extreme or deviant case sampling examines people who deviate from the norm. You can think of this as the inverse of typical case sampling.

Your representative sample comes from a particular situation. On the other hand, extreme case sampling examines the general population that reacts to a certain trend.

You want to know how study habits help high achievers in school. This type of purposive sampling will involve talking with students with high marks.

Sampling of critical cases

This type of purposive sampling is more targeted than the two previous ones. In effect, this reduces the selection of the sample into several categories.

For example, the sociologist CJ Pascoe wanted to study gender identity and sexuality among high school students. It was then that she used critical case sampling.

She chose students who matched the characteristics of average high school students in terms of population and family income. She chose critical case sampling, so her findings apply to the general population.

Total population sampling

You want to know how a certain event affected certain groups of people within a population. Maybe you want to see how COVID-19 has affected the lives of elementary and high school students.

You sample the total population by collecting data from all members of both groups. Then you compare the results with each other.

This way you can see if they had shared or isolated experiences. As you can see, your choice of purposive sampling method will depend on the research objective.

Expert Sampling

This is the type of purposive sampling that researchers use before conducting a study. Expert sampling involves obtaining information from people who are knowledgeable about a certain topic.

Researchers need this kind of purposive sampling if they don’t know enough about a topic. Or they need more information about it that they can’t find in most resources.

You could say it wastes time. If you look closely, expert sampling allows you to collect data much faster than without. The information you have collected can tell you what information you need.

Advantages of purposive sampling

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  • This saves time and money. As mentioned earlier, it lets you work with your budget and schedule.
  • Purposive sampling allows you to get the most information from a small population.
  • Purposive sampling allows researchers to collect responses for qualitative research, in order to obtain more precise results.
  • It ensures that the data you have collected is relevant to your study.
  • Purposive sampling allows you to target niche audiences for your research.
  • It also reduces the margin of error because you can get rid of irrelevant information.

Disadvantages of purposive sampling

  • The reasoning behind your sample selection may turn out to be invalid.
  • You could exclude subsets that you needed, which would skew your search.
  • Purposive sampling participants can manipulate the data. For example, they might not answer questions honestly. Therefore, your purposive sampling returns invalid results.
  • Purposive sampling may not be the best way to collect information from a large population.
  • You can’t really eliminate bias when selecting respondents.

Final Thoughts

Purposive sampling allows you to choose the right research topics. This way you can gather the right data for your study. It’s far from perfect, however.

You and your respondents can cause research errors. This is because you may apply your biases to a study while respondents may provide inaccurate answers.

You cannot remove the margin of error, only reduce it. This is why planning is important in any search. Once you find one on the internet, watch how the experts put together their data.

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