What is Systematic Sampling in Surveys?

Surveys help us understand what people think and need, from shopping habits to opinions on big issues. 

But how do we get this information? We use systematic sampling techniques to take a peek into a large population without having to ask everyone. 

It’s hardly possible to talk to millions of people! Instead, we use smart shortcuts like systematic sampling. 

It gives us a fair and accurate picture by selecting people in a regular pattern. So, why should you care? 

Because the better we sample, the more we can trust what surveys tell us. 

Today, we will discuss systematic sampling and see how it powers up our surveys!

Systematic sampling: what is it? 

Systematic sampling is a way to pick out members from a big group with a neat and structured plan. 

Think of it as a probability sampling method, carefully picking people in a step-by-step way. 

It starts with a random starting point in the population list and keeps picking every nth person. 

The distance between each person picked is the sampling interval, which we figure out by dividing the population size by how many people we want to include (sample size). 

Then, everyone in the entire population has a fair chance of being selected.

Let’s break it down with a systematic sample example. ⬇️

You have 1000 people and want to understand 100 of them. Your sampling interval (n) becomes 10. So, after choosing a random starting point, you pick every 10th person to be part of your group.

💡 Not quite sure how to survey people? SurveyLab is a great tool with many templates to choose from!

Why choose systematic sampling? 

There are many pros, but cons can be found as well. Let’s start with the advantages. 

Simplicity and efficiency

Systematic sampling is a favorite for many because it’s simple and efficient, especially with many people. Its linear path makes it less of a headache than other sampling methods like stratified random sampling or cluster sampling.

Less susceptible to data manipulation

The design of systematic sampling reduces the risk of data manipulation, since the only random sample is choosing the starting point. 

It’s tough to mess with the data, making it less likely for data manipulation compared to methods like simple random sampling.

Uniform coverage of the population

It makes an even distribution across everyone, so no group is left out or overly focused on.

Considerations in systematic sampling

Go through this list to be aware of the disadvantages systematic sampling may have.

Risk of periodic patterns

One hiccup can be repeating patterns. If the group has a certain order that matches the sampling interval, systematic sampling might accidentally favor or ignore some parts, not giving a truly representative sample.

Inflexibility

Once you set your path, there’s not much wiggle room. This might not work for every research type, particularly those that need a flexible approach.

Steps involved in systematic sampling

Check out the steps you need to take to understand how systematic sampling works. It will be easier for you to start, then.

#1 Define the target population and determine sample size

Before starting with systematic sampling, pinpoint who you want to study (the target population) and decide on the number of people you’ll include (sample size). 

Know the total population size and what part you’re interested in. Your desired sample size should be big enough to reflect the entire population but small enough to handle easily and affordably.

#2 Calculate sampling interval

Next up is figuring out the sampling interval. To do that, divide the population size by the sample size. 

➡️ Let’s say your total is 1000 people, and you want a group of 100, the sampling interval would be 10. So, you’ll include every 10th member of population in your sample.

#3 Select the starting point

The starting point is where you begin picking people, and it’s the only random component in systematic sampling. 

You randomly choose a number between 1 and the sampling interval.

➡️ For example, if your interval is 10, your starting point could be any number from 1 to 10.

#4 Ensure randomness in the starting point

To keep the process fair, the starting point needs to be randomly picked. This is usually done with random number generators. 

➡️ It’s important because it gives everyone an equal probability of being chosen, which helps avoid any bias.

#5 Address potential bias

Sometimes, systematic sampling might accidentally line up with a hidden pattern in the group, which can skew results. 

Read more here: What is Non-Response Bias and Why It Matters?

➡️ Check for these patterns and adjust your approach if needed. You might change the interval or switch to a different sampling method.

#6 Combine with other sampling methods

To get around some of the systematic sampling’s limitations, you might mix it with other techniques. 

➡️ For instance, stratified random sampling can be used first to divide the group into smaller, varied parts. It may help your final sample represent everyone.

#7 Set limitations and mitigation strategies

While systematic sampling is usually efficient and easy, it’s not perfect. 

Watch out for any repeating patterns in your group that might affect your results. 

➡️ Researchers often need to tweak the sampling interval or starting point, or use other methods to get a truly representative sample.

Comparing systematic sampling with other sampling techniques

See how different methods measure up, including our focus on systematic sampling.

Systematic sampling vs simple random sampling

When exploring the sample selection process, let’s first compare systematic sampling with simple random sampling.

Systematic sampling	Simple random sampling
➕ A probability sampling method where sample members are selected at regular intervals from a sorted population list.  ➕ Effective and simple, especially for a larger population.  ➖ There is a risk of data bias with periodic patterns in the population.	➕ Involves selecting individuals randomly from the entire population, giving each member an equal probability of being chosen.  ➕ Ideal for avoiding biases.  ➖ Less practical for large datasets due to the complexity of randomly sampling each individual.

Systematic sampling vs stratified random sampling

How does systematic sampling contrast with stratified random sampling in the sample selection process? Check out the comparison.

Systematic sampling	Stratified random sampling
➕ Selects individuals at predetermined intervals from a list, and makes it simpler and faster.  ➖ Potentially less representative of all segments of the total population.	➕ Divides the total population into distinct subgroups and sample randomly from each subgroup.  ➕ Ensures all population segments are represented in the sample, suitable for diverse populations.  ➖ Requires a comprehensive understanding of the population’s characteristics.

Systematic sampling vs cluster sampling

Look at systematic sampling alongside cluster sampling in our discussion of the sample selection process.

Systematic sampling	Cluster sampling
➕ Offers a more straightforward approach by selecting individuals at regular intervals from a list. ➖ May miss nuanced representation achieved through cluster sampling, especially in diverse populations.	➕ Involves dividing the population into clusters and then randomly selecting entire clusters for the sample.  ➕ Works for geographically spread-out populations.  ➖ May increase sampling error if clusters are not homogeneous.

Systematic sampling vs linear and circular systematic sampling

Compare systematic sampling with its variations – linear and circular systematic sampling.

Systematic sampling	Linear and circular systematic sampling
➕ A probability sampling method that selects sample members at regular intervals from a complete list.   ➕ Maintains a low-risk factor. It’s straightforward and efficient, especially for data collection from a complete list of the population.	➕ Linear systematic sampling selects at regular intervals from a linear list.  ➕ Circular systematic sampling treats the list as circular, looping back to start. ➕ Useful in avoiding risk of data bias at the end of the list.  ➕ Both maintain the low-risk factor inherent in systematic sampling ➖ May overlook patterns present in the population.

Suitability of systematic sampling for specific research scenarios

Systematic sampling works great in situations where you need to pick sample members from everyone or a large group, like when collecting customer experience feedback. 

It helps researchers form samples at fixed steps, and it makes the whole process tidy and predictable. 

But, be careful if the people or things you’re studying change a lot or follow a repeating cycle. In these cases, systematic sampling might accidentally lean one way, missing important information.

In general, systematic sampling is loved for being straightforward and efficient in data collection, particularly with big groups.  Ensure the people you pick truly reflect the whole group you’re studying, especially if there’s a chance that some kind of pattern could throw off your results.

Examples of systematic sampling in surveys

It’s a popular method in many areas, for example:

➡️ Market research

Systematic random sampling is a popular method in market research. Businesses use it to figure out what customers think. 

Picture a company checking on how happy people are with what they sell. They grab their customer list and pick every nth person based on the sample interval to get a feel of everyone’s views. 

Why does it work? 

The even spread ensures all parts of the larger population, particularly the target audience, are considered, minimizing bias.

➡️ Social sciences

In social sciences, systematic random sampling is understanding big groups and what they do. 

Let’s say researchers want to explore who’s voting for whom in a city. They use systematic sampling to pick households at regular sampling intervals across different areas. 

Why does it work? 

They make sure to include a mix of opinions and lifestyles, giving a real picture of the city’s heartbeat.

➡️ Opinion polls

For opinion polls, especially those covering a larger population, systematic sampling is the go-to method. 

Pollsters looking into political trends might start with a voter list and select people at fixed gaps, known as sampling intervals. 

Read also: Types of Poll Questions You Can Ask.

Why does it work? 

It’s great for getting a pulse on the entire voting population, all while keeping things straightforward and maintaining a low risk of bias.

Benefits of using systematic sampling

It’s a solid way to gather reliable data from a big group of people. Because of the regular intervals, every part of the group has a chance to be heard, which is super helpful for maintaining accuracy. 

It’s not complicated to use, making it a friendly choice for many. Still, it’s good to keep an eye out for any sneaky biases, especially in groups where patterns might throw off the randomness. And that’s crucial in data collection processes where gathering representative systematic samples matters.

Best practices for systematic sampling

Stick to a set of best practices to make your results accurate and reliable. 

01 Figure out the right number to study

Before jumping into systematic random sampling, determine the right number of people to look at (that’s your sample size). You want enough people to give you the real story, but not so many that it’s unmanageable. 

Also, consider the total number of people (population size) and how precise you need to be. Use tools and formulas available out there to help you get the numbers.

02 Choose an appropriate sampling interval

How often you pick a member of the population is your sampling interval. This number depends on how big the group you’re studying is. 

Bigger group? Bigger gaps between picks. Divide the total population size by your sample size.

03 Select a random starting point

It’s got to be random to make sure you’re not leaning any particular way. Most people use a random number generator for this. All to give every single person an equal shot at being included.

04 Ensure transparency and documentation

Document every bit of your process, from figuring out your sample size to choosing your starting point. Clear records mean your work is transparent and can be double-checked. It makes everyone trust your findings and might even help you spot any slips or areas for improvement.

05 Consider potential sources of error

Sometimes, the group you’re analyzing might have its own natural rhythm or repeating pattern that could mess with your results. If you notice this happening, you might need to switch up your interval or try other methods to keep things unbiased.

Read also: Margin of Error in Surveys: What is it and How to Tackle it?

06 Combine with other sampling techniques if necessary

There are times when you might need to blend in other sampling techniques to get a fuller picture. This is especially true if you’re looking at a diverse crowd or need to make sure certain groups are included.

Read also: Probability Sampling: Methods, Examples, Differences, and Insights.

07 Check things out yourself

If possible, physically observe the group you’ve sampled. It’s a good way to verify that your sample is a true mini-version of the whole crowd under study.

08 Adapt and adjust

Things change, and so might your sampling method’s effectiveness. Keep an eye on it and be ready to adjust as needed to ensure it’s always giving you the best snapshot of the population.

Conclusion on systematic sampling

It’s time to draw conclusions.

Remember, the goal of systematic random sampling is to get a sample that really represents the entire population without any bias. It’s giving every person an equal shot at being included and making sure no particular pattern or group is left out or overrepresented. 

Keep our best practices and other tips in mind, and you’ll be on your way to collecting and analyzing data that’s both reliable and insightful.

And for easy surveys, use SurveyLab! Sign in to start for free.

FAQ on systematic sampling

Go through the questions, so you have a clear picture of the topic.