Understanding the Pros and Cons of Longitudinal Studies
April 1, 2025Trying to gather feedback from every current or future consumer is impossible. That is why market research employs various sampling techniques (depending on the research method) to try and capture a sample of people that can represent the larger population.
What is Market Research Sampling?
Market research sampling is a process that is both an art and a science. It aims to pinpoint a carefully chosen subset of individuals to act as representatives for a much larger population. When executed precisely, this select group and the insights they provide should serve as a reliable mirror reflecting the characteristics, preferences, and behaviors of the broader population. In essence, a well-constructed sample becomes the key that unlocks a deeper understanding of your target audience, enabling businesses to make informed decisions that resonate authentically with their customers. Sampling is the cornerstone of robust market research, ensuring that the findings are informative and represent the market landscape.
Why is Market Research Sampling Important?
Market research sampling is of paramount importance because it is the keystone to truly comprehending your target audience. When you obtain the right sample for your research project, it opens the door to a deeper understanding of your audience’s needs, attitudes, behaviors, and preferences. Moreover, it provides a valuable source of feedback on your product and/or service that can be used to refine and tailor your offerings. The data gleaned from the insightful responses of your carefully selected sample empowers your organization to make not just decisions but better, more informed decisions that resonate with your audience and drive success in an ever-evolving marketplace. Sampling is the compass that guides your research voyage, ensuring you navigate in the right direction toward meaningful insights and impactful outcomes.
Market Research Sampling Techniques
In the world of market research sampling, there are a wide variety of techniques and methodologies that researchers can employ to gather a representative sample of the population to gain insights from. Here are a few of the more frequently used techniques for sampling in market research:
Random Sampling
Random sampling gives every individual within a population an equal opportunity to be selected for the study. This approach to probabilistic sampling diligently eliminates any lurking biases associated with the target audience, as no one is favored or more likely to be chosen over another. By bestowing each member of the population with the same chance of being part of the sample, random sampling not only ensures fairness but also bolsters the reliability and representativeness of the collected data, ultimately reinforcing the robustness of your research findings.
Systematic Sampling
Systematic sampling offers a structured and efficient approach to the art of sampling. In this method, members of a population are meticulously chosen at a consistent and predetermined interval, forming a sample that accurately represents the entire population. This systematic approach simplifies the sampling process and ensures that the selected individuals maintain a balanced and coherent distribution, providing researchers with a reliable cross-section of the population’s characteristics and behaviors. By its methodical nature, systematic sampling strikes a harmonious balance between simplicity and representativeness, making it a valuable tool in the researcher’s toolkit for generating robust insights.
An example of sampling methodology would be if you wanted to survey a population of 20,000 people, you would select every 200th person to be part of your pool of respondents.
Stratified Sampling
Stratified sampling is a method that adds a layer of sophistication to the sampling process. In this approach, the population is thoughtfully segmented into smaller, homogeneous subgroups known as strata. These strata are defined based on shared characteristics or attributes such as job function, income level, or any other relevant criteria. By creating these distinct strata, researchers can ensure that each subset is accurately represented in the sample, allowing for a comprehensive understanding of the entire population. This meticulous method of sampling empowers researchers to obtain a sample that not only captures the diversity within the population but also provides granular insights into each stratum, making it an indispensable tool for gathering nuanced and meaningful data.
Quota Sampling
Quota sampling represents a refined extension of the stratified sampling technique. This method makes the research process even more deliberate as specific quotas are established within each population stratum. These quotas serve as predefined benchmarks, ensuring that the sample meticulously mirrors the characteristics of the larger population. By meticulously assigning quotas, researchers go the extra mile to guarantee that the sample encompasses the diversity within each stratum and the correct proportions of individuals from different segments. Quota sampling is a method characterized by its dedication to representativeness, making it an invaluable approach for obtaining a sample that accurately mirrors the intricacies of the broader population.
Cluster Sampling
Cluster sampling shares similarities with stratified sampling as it involves the division of a population into clusters or groupings. However, in this method, researchers take a distinct approach by randomly selecting specific clusters as their market research sample. The objective is to ensure that each chosen cluster serves as a microcosm, accurately reflecting the characteristics of the broader population. An illustrative example of this approach could be seen in examining school districts: rather than surveying every student, researchers might randomly select a few school districts, recognizing that these clusters should ideally provide insights that generalize to the entire student population. Cluster sampling offers an efficient way to capture the diversity within a population while managing the logistical complexities that can arise when dealing with large and dispersed groups.
Area Sampling
Area sampling is a type of sampling that is defined by geographical boundaries. This form of sampling is commonly used for geographic or ecological sampling. If it is used to gather insights on human behavior, it should be combined with some form of cluster or stratified sampling so that you do not end up trying to gather samples from a sparsely populated area.
Determining the Right Sample Size For Your Market Research
Determining the right sample size for your online quantitative research project, or any market research project, is crucial for obtaining statistically reliable and meaningful results. Here are a few steps to help you determine the appropriate sample size you need for your research study:
Define Your Research Objectives
Start by clearly defining the objectives of your research project. What specific questions do you want to answer, and what are your research goals?
Understand Your Population/Target Audience
Before diving into sample selection, market researchers must clearly understand the population they want to study. This first step will shape every decision in the sampling process. A well-defined population provides clear boundaries for who should be included or excluded from your market research sample, helping avoid potential blind spots that could compromise your findings. Additionally, understanding your population size is essential for calculating your sample size.
Population definition requires careful consideration of various demographic, behavioral, and psychographic characteristics. For example, a luxury automotive manufacturer conducting market research might define their population as “high-income professionals aged 35-65 in metropolitan areas with annual household incomes exceeding $150,000.” This precise definition helps researchers understand exactly who they need to include in their sample.
The population definition should align closely with research objectives while remaining practical and accessible. Consider factors like geographic boundaries and limitations, demographic characteristics, behavioral patterns relevant to the research, psychographic profiles, and your time frame for data collection.
Related: What is longitudinal data?
Deciding on a Sample Size
Once you know your population, you need to decide how many people to include in your sample. This is your sample size. A bigger sample size usually gives more accurate results, but it also costs more money and takes more time. The key is finding the sweet spot where your sample is large enough to be statistically valid but is still manageable.
Several factors influence optimal sample size determination:
- Population size and variability
- Desired confidence level
- Acceptable margin of error
- Expected response rate
- Resource availability
- Time constraints
For quantitative research, statistical calculations can help determine the minimum sample size needed for reliable results. However, qualitative research often requires smaller samples, focusing instead on depth of insight rather than statistical significance. For example, focus groups exploring consumer perceptions might only need 8-12 participants per group, while a national consumer survey might require several thousand respondents to achieve statistical validity.
Select Your Confidence Level and Margin of Error:
Choose a confidence level (typically 95% is used) and a margin of error (usually expressed as a percentage). The confidence level represents how confident you want your sample’s results to reflect the actual population, and the margin of error indicates the acceptable level of deviation from the true population parameter.
Estimate Population Variability:
You’ll need an estimate of the variability or standard deviation within your population. If you don’t have this information, you can use a conservative estimate or conduct a small pilot study to gather data. You can also ask your sample provider; they may be able to answer this based on previous studies to similar audiences they have conducted. Many use 0.5 as a constant.
How to Calculate Your Needed Sample Size
Here is the formula to calculate the sample size you will need for your market research project:
Necessary Sample Size = (Z-score)² * StdDev*(1-StdDev) / (margin of error)²
Calculated Sample Size Examples
Here are a few examples for calculating sample size (based on some basic assumptions.)
Example 1:
- Margin of error: 5%
- Confidence level: 80%
- Recommended sample = 165
Example 2:
- Margin of error: 5%
- Confidence level: 90%
- Recommended sample = 271
Example 3:
- Margin of error: 4%
- Confidence level: 95%
- Recommended sample = 600
Example 4:
- Margin of error: 2%
- Confidence level: 99%
- Recommended sample = 4,130
Want to calculate the actual sample size you may need? Click the button below and we can help!
Choosing a Sampling Technique
The last step is choosing your sampling technique. When you conduct market research, you’ll need to decide between probability and non-probability sampling methods. Probability sampling gives everyone in your population an equal chance of being picked. Non-probability sampling doesn’t.
Say a national brand is conducting brand awareness research across different regions. They need to be sure they’re hearing from all types of customers in every area, so they would use probability sampling. But if you’re a local business testing new product concepts or doing quick market segmentation research, non-probability sampling might work just fine. You’ll get useful insights faster and spend less money, even if the results aren’t as statistically precise.
Probability sampling takes more time and money but gives you results you can bank on. This is particularly true for longitudinal research, where maintaining sample consistency over time is crucial. Non-probability sampling is sufficient when you need quick feedback, or your target group is hard to reach.
Related: The pros and cons of longitudinal studies
Ensuring Representative Sampling
Getting a truly representative sample is essential in market research. It helps avoid blind spots and ensures accurate results. This representativeness depends not only on sample size and sampling technique but also on careful attention to demographic balance, geographic distribution, and other relevant characteristics that might influence research outcomes. A good sample leads to better insights into consumer behavior and customer satisfaction.
Avoiding Sampling Bias
Sampling bias represents one of the most significant challenges in sample selection. It occurs when certain segments of the population are systematically over- or under-represented in the sample, leading to skewed results that don’t accurately reflect the target population.
Common sources of sampling bias include:
- Selection bias – When certain groups are more likely to be chosen than others
- Non-response bias – When particular segments are less likely to participate
- Coverage bias – When the sampling frame doesn’t adequately represent the population
- Voluntary response bias – When participants self-select into the study
To minimize sampling bias, researchers should employ multiple strategies:
- Employ a strategic sample blending approach
- Monitor response patterns
- Apply statistical corrections when necessary
For example, a national bank doing customer surveys might notice they’re getting mostly responses from older customers. To fix this, they could use targeted online surveys to reach younger age groups. They might also use ethnographic research to understand why some groups aren’t responding.
Balancing Diversity and Relevance
A good sample needs to be both diverse and relevant. Diversity ensures that different views are included, while relevance ensures that the sample fits the research goals. This balance is key for accurate market research.
This balance can be achieved through:
- Careful screening criteria development
- Quota controls for key demographic variables
- Regular monitoring of sample composition
- Adaptive sampling strategies
- Targeted recruitment methods
Enhancing Data Quality from Market Research Samples
The quality of market research insights depends heavily on the quality of the data collected from the sample. This requires attention to both the collection process and verification procedures to ensure the reliability and validity of the findings.
Incorporating Survey Responsive Rate
The survey response rate tells you how many people actually completed your survey compared to how many received it. Getting a good response rate means better data and fewer gaps in your research. The key is making your survey appealing and easy to complete. Keep questions clear and straightforward — avoid jargon or complicated language that might confuse people. Mix different types of questions to prevent survey fatigue. You might start with simple yes/no questions, then use rating scales, and include a few open-ended questions for deeper insights.
The when and how of sending surveys matters a lot. Choose times when your target audience isn’t too busy, avoiding holidays or typical vacation periods. For business surveys, mid-week mornings often work best. For consumer research, early evening might get you more responses. Don’t forget about making your survey mobile-friendly. These days, most people check everything on their phones first. If your survey doesn’t work well on mobile devices, you’re likely to lose a lot of potential responses.
Getting people to participate often means offering something in return. Smart incentives can boost your response rate significantly. This might be store credits, gift cards, or a chance to win something valuable. Just make sure your incentive doesn’t accidentally attract people outside your target audience or influence how they answer. The goal is to encourage participation from your true target population. A higher response rate usually means more reliable data for your market research sample, as long as those responses come from the right people.
Utilizing Data Verification Techniques
Making sure your data is accurate is a critical part of market research. Without good data verification, you might end up making business decisions based on faulty information. The key is having a solid system to check that the responses you’re getting are real and reliable. One important step is using screening questions. These help ensure you’re talking to people who actually fit your target audience and can provide meaningful insights about your topic.
Quality check questions are another powerful tool in your verification toolkit. These are carefully designed questions that help identify respondents who aren’t giving honest or thoughtful answers. For example, you might include an attention check that asks respondents to “Select ‘strongly disagree’ for this question.” If they choose any other answer, it signals they might not be reading questions carefully. Similarly, asking questions with obvious answers helps spot automated responses or people rushing through your survey.
Looking at patterns in your data is equally important. This means checking if responses make logical sense together. For instance, if someone claims to be a senior executive but reports an entry-level salary range, that’s a red flag. Or if their answers to similar questions completely contradict each other, you might need to take a closer look at their responses. These inconsistencies can help you identify questionable data before it affects your results.
Using verification methods makes your market research samples stronger and more trustworthy. When you have clean, verified data, you can be more confident in your findings. This leads to better decision-making for your business, whether you’re developing new products, adjusting your marketing strategy, or understanding customer needs.
EMI – Your Market Research Sample Experts
EMI is pretty unique in the online market research sample industry. As a leading sample consultancy, we understand the entire sample landscape, not just a single panel. Our goal is to create a strategic blend of samples based on your project rather than make your project fit any specific panel. Unlike most market research sample panels, EMI doesn’t own a panel. That means we are not biased toward a specific panel asset. We create strategic sample blends that best fit the goals of your research, not what best fits any panel we might own.
Over the last 20 years, we have developed a knowledge of the online market research sample industry that is unrivaled when combined with our unbiased sample blending approach. We have built this knowledge by not only working with panel partners throughout the industry but also conducting research-on-research for more than a decade into the online sample industry to understand the differences between consumer panels, and how they change over time.
This unparalleled industry knowledge is the driver, along with not owning our own panel, to provide unbiased, transparent sample consulting and advice to our clients that puts the emphasis on what is right for their research, and not what is right for any specific panel.
Ensuring Data Quality For Market Research Sample
EMI has been dedicated to the pursuit and delivery of high-quality, actionable data on behalf of our clients for more than 20 years. This commitment to quality comes from our extensive industry knowledge and our drive to deliver unbiased, actionable quantitative data tailored to the needs of our clients. To do that, we have built a multi-faceted suite of quality measures, including both technological and human elements, to provide the highest quality data possible.
Human Elements
- Partner Assessment Process
- Dedicated Quality Committee
- Response Red Flagging System
- Screener and Questionnaire Design Expertise
- Research-on-Research
Technology Elements
- SWIFT (Proprietary Digital Fingerprinting and De-Duplication)
- Advanced Bot and Fraud Detection
- AI-Powered Data Scrubbing
- Geo-IP Blocking
- Quality Optimization Rating for Sample (QORs)
- Cross-Panel Block List
Quality Optimization Rating for Sample
The Quality Optimization Rating for Sample, or QORs, is EMI’s proprietary sample quality metric used to evaluate the quality of the sample that we provide to our clients. It was developed to ensure that EMI’s team of expert consultants have access to data-driven insights to craft solid sampling strategies for the most optimal quality experience for both our clients and panels. EMI’s Quality Optimization Rating considers pre-study traffic health, in-study participant behaviors, and post-study data validity consistency. This metric aids in monitoring and tracking over time how well a panel partner performs within Consumer, B2B, and Healthcare work, both domestically and globally.
Get more details here.
EMI’s Approach to Sampling
Strategic Sample Blending
Strategic sample blending takes traditional blending to the next level and is the best sample design to ensure confident business decisions. It is blending three or more sample providers, but the selection and blending of the selected providers is done in an intentional and controlled manner. Providers are selected to complement one another, while reducing the overall sample bias and any potential behavioral or attitudinal impacts a panel can have. This method ensures that sample blending isn’t done simply for blending’s sake. Utilizing our strategic methodology, we build customized blends that best meet clients’ needs while ensuring the best results possible.
Additionally, by strategically selecting providers and managing their allocation, you increase overall feasibility while avoiding “top-up” situations and panel bias, both of which can skew your data.
EMI’s Online Market Research Sample Panel Network
EMI has built a global network of sample partners that gives you access to one of the highest quality pools of respondents of varying demographic, socio-economic, geographical, behavioral, and psychographic characteristics. This gives EMI the ability to create strategic sample blends that best fit your study and provide you high-quality, deep insights that you need to make better business decisions.
Every market research sample panel in our network has passed our rigorous Partner Assessment Process so we can best understand the recruiting methods, validation process, and other data quality measures they have in place, as well as the ins-and-outs of their panel. Our strict vetting process ensures we only allow the best sample providers into our network and that we maintain a high level of data quality for our clients.
World-Class Project Management
We don’t just provide you with custom consumer sample solutions, we back it up with our world-class project management services. The team provides 24/7/365 coverage and works with you as an extension of your team, providing you a single point of contact, utilizing responsiveness, creativity, and flexibility to help you navigate any issues.
The backbone of all projects is SWIFT, EMI’s proprietary, cloud-based, sample management platform. By connecting your survey to our sample network, we are enabled to:
- Launch your projects.
- Field and close projects with more speed and accuracy than other panels.
- Manage multiple partners where we can insure there are no duplicates across panels.
You can view the full capabilities of SWIFT here.
EMI’s experience in identifying, vetting, and managing a network of high-quality market research sample panels, combined with our industry-leading approach of strategically blending samples, makes us your best option for conducting market research. We will offer your company unique insights that will allow you to uncover exactly who your customer is, how they buy, and why their behavior changes over time. These insights will help you develop your company’s strategies and grow your business.
EMI’s unique combination of expertise, white-glove service, and reach allows us to be your one-stop sample provider — getting it done without compromise.