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5 reasons to use a longitudinal study

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Getting insight into people’s opinions, preferences, and habits is extremely valuable for your business. You can gain a deeper understanding of what your target audience or potential new markets think about your industry, products, services or brand. 

One of the most common ways to measure these sentiments is to ask a group of people how they feel at a certain moment in time—you send out a survey or conduct an interview to gather feedback from customers or employees, and then act on that information. And this method works pretty well for a variety of purposes. 

But we live in a fast-changing world, and people’s opinions and preferences shift over time. In order to gain the most accurate insights and data, your methods of studying what consumers and employees want should be able to track those changes as they happen so you stay on top of any trends that could impact your business. 

This is where longitudinal studies are vital for companies—they allow you to check in with your audiences regularly and proactively. There are many benefits of longitudinal studies for businesses, and we’ll cover what you need to know and the five top reasons you should use them in this article.

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Longitudinal studies 

What is a longitudinal study? It’s a type of research study that involves consistently collecting feedback and information from the same group of people over a longer period of time. This period of time could be weeks, months, years, or even decades. 

Running longitudinal studies takes more time and effort than short-term cross-sectional studies because you must repeatedly ask a specific group of people for information and opinions and preferences. But this effort pays off, as longitudinal studies allow you to gain unique insights and track changes over time in your customers or employees. 

What are the benefits of a longitudinal study? There are many—and we’ll cover the most important ones below. 

How a longitudinal study works

Longitudinal studies examine a set of variables over a period of time, as opposed to cross-sectional studies that look at multiple variables at one moment in time. Longitudinal studies repeatedly check in with the same people over a longer period of time, allowing you to track changes in opinions or behaviors. 

For example, you can design your longitudinal study to ask a select group of customers about how satisfied they're with a particular product you offer, or about your brand reputation, or their marketing preferences and brand awareness. Market research studies are especially effective in longitudinal form, as they help you stay on top of your customers’ preferences even as they shift over time. And you can also create employee surveys that check in regularly with your workers about their engagement levels and opinions about your workplace culture. 

You can choose to segment your study audience in multiple ways. Segmenting your customers allows you to personalize your survey questions effectively and gain more actionable and accurate insights. Some common segments include: 

  • Region
  • Industry
  • Spending level 
  • Purchasing a specific product or service 
  • Goals for using a certain product or service 
  • Job role or department

Types of longitudinal research 

There are three major types of longitudinal studies that your business can conduct when undertaking a research project or gathering data from your customers, prospects, and employees. 

Panel study

Panel studies involve surveying a cross-section (also known as a sample) of people from a larger population. Market research panels will recruit people to take surveys and allow you to target the exact profile you need to reach. In some cases, you’re able to recontact the same group of people over a specified period of time to see if their views and desires change. If you cannot go back to the same exact group of people every period, you can use panels to sample the same profile of people each time. 

Cohort study 

A cohort study involves selecting a specific group of people who have something in common—their age, their region, their income level, or their job role, for example. 

Retrospective study

As their name suggests, retrospective studies are conducted by looking at historical information such as pre-existing records. 

All three of these longitudinal study types are useful, but you will want to be sure to pick the one that works for your study goals. 

Tips for creating surveys for longitudinal studies

Here are four tips to help launch your longitudinal studies:

  1. Stick to a timeline. Determining the right length of time for your longitudinal study depends on your goals and what is reasonable. However, sticking to a study timeline of several weeks to one to two years will allow you to gather the data you need. 
  1. Once your timeline has been determined, you should also think carefully about how often you will send surveys to your audience. A good rule of thumb is that you can survey people more often if you have a closer relationship with them. For example, a manager can survey an employee monthly, and you can survey loyal and engaged customers quarterly, but stick to less frequent surveys for groups of people who don’t have much of an existing relationship with your business. They won’t respond often, but they'll get annoyed quickly if you ask them for data and opinions too often. 
  1. To ensure your longitudinal study is as accurate as possible, stick to asking exactly the same questions each time you survey your participants. Even small changes to question-wording can change the answers of your survey respondents, and that means the trends you notice might not be quite on target. 
  1. And remember, creating a perfect longitudinal study simply isn’t possible. Some of your study subjects will move, change jobs, retire, or undergo other life changes that cause them to either drop out of your survey or no longer be a good fit. That’s why adding more people to your survey group at the start than you need is a best practice. But consistently surveying a sample of people over a period of time will still give you essential insights your business needs to thrive. 

Why do a longitudinal study at all? They take more time and typically cost more money than conducting a cross-sectional survey. But they have many benefits that you can’t get using other study methods, and these make a compelling case. Need further convincing? Here are the five top reasons to use a longitudinal study for your business. 

Reason 1: Allows researchers to look at changes over time 

There are many ways to find out how people feel, think, and behave at a certain point in time. But those survey and interview options, while they can provide valuable insights, also have blind spots. People change their thoughts and behaviors over time—and those shifts can happen rapidly in our fast-changing world. Suddenly your business can get left behind following what you thought was the right path, based on information you gathered from customers or employees years ago. 

To keep up with industry trends, changing consumer behavior, and technological advancements, these studies allow you to track changes over time with a high degree of accuracy. These studies allow you to gain unique insights that other methods simply can’t offer, and they'll help your business thrive as a result. 

For example, your company might offer several software as a service (SaaS) products. They have features that no other competitor had when you entered the market, and customers initially loved what you offered to them. If you simply sent out cross-sectional surveys to check in on satisfaction rates, you might think customers are still pretty happy. 

But if you had also conducted a longitudinal survey to see how your original customers’ satisfaction levels changed over time, you could check in regularly to see how that group grew more or less satisfied with your product the longer they use it. That data can provide valuable insights into what your products are delivering now—are they still providing value and a good customer experience, or are customers unhappy because your features haven’t kept up with other, newer options in the market? 

Reason 2: High accuracy when observing changes 

When tracking trends over a longer period of time, it can be tempting to conduct a series of cross-sectional surveys asking large groups of people about their views and preferences. It’s simpler to set up than a longitudinal study, and at first glance, the results can seem similar. 

However, longitudinal studies offer more accurate data because you’re comparing the same people’s views over a period of time. Cross-sectional surveys have their uses, but repeatedly surveying different groups of people will not give you a fully accurate picture of how their views changed. Your study data could be inaccurate because you’re asking two or more groups of people who may already have very different views to provide insights and comparing them—but changes you see might be an existing group preference, not a shift in views. 

In an advertising study, for example, you could track brand trends by asking your study participants about their level of brand awareness or their thoughts on your brand reputation quarterly for a year. If you see awareness growing or your reputation improving, you know that these are real trends since the same group saw a shift. 

However, if you simply conduct quarterly cross-functional surveys instead, you might see changes but won’t know if they really reflect a true shift in brand tracking or just different levels of awareness among the surveyed groups. Your cross-functional surveys might have reached a group that consumes a lot of tv in the first quarter and another group with very different media consumption habits in the second, which could significantly affect the quality of your data.

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When you need highly accurate data, longitudinal studies are the way to go. You’ll have confidence that the trends you see are correct and can make business decisions accordingly. 

Reason 3: Establish a sequence of events 

Longitudinal studies allow you to follow your study subjects in real-time, which offers valuable information. They can give you insights into the true sequence of events that occurred when a customer is taking action or forming an opinion, and the same is true for employees as well. 

In fact, employee engagement and satisfaction can be measured reliably using a longitudinal study. Let’s say your business wants to learn how a new policy you will be implementing affects employee happiness. You can survey a segment of employees before the change occurs to establish a baseline and then ask them again after the change is made and then again a few months later after the change has been in place for some time. 

By conducting a survey to determine the effects of the changes, you will have confidence that your data accurately reflects a cause-and-effect relationship between the policy and the happiness of your employees. Without a longitudinal survey, you’re left guessing as to whether the policy is causing these changes or something else completely unrelated. 

Reason 4: Define causal relationships 

Since these studies follow the same group of individuals over a set period of time, researchers can establish a clear sequence of events. And with this accurate event view, you can also define causal relationships between actions and opinions or preferences. You will have a clear understanding of the cause-and-effect relationship in events and make business decisions confidently. 

Causal relationships are often difficult to measure, and that can be a challenge when running a business. You want to find out if a recent pricing change made customers more or less likely to renew, or if a product update leads to greater customer churn or an increase in satisfaction, or if a new employee appreciation program is causing higher employee engagement rates. With cross-sectional surveys, you can gather information on satisfaction and retention, but you won’t know for sure if increases or decreases are actually caused by the changes you’ve made or if they’re related to something else entirely. 

But with the power of longitudinal studies, you can track feelings and opinions over time, allowing you to determine with increased certainty what events were behind any changes. You can survey your study participants before and after you make a change to products or policies, and the data will confirm or exclude a causal relationship. And since these studies ask participants about something happening at the time, instead of an event in the past, you’ll know the data and feedback you receive are timely and accurate. 

Reason 5: Exclude recall bias 

Longitudinal studies follow participants in the moment to form a highly accurate picture of events and causal relationships. On the other hand, studies that ask participants to remember experiences, feelings, and preferences from the past have a tendency to be inaccurate because of recall bias. Recall bias happens when study participants are systematically more or less likely to remember or report things that happened to them or their feelings and opinions because they're in the past to some degree. 

It’s a natural human tendency—our views of our past experiences and feelings are difficult to recall accurately because they’re colored by our current way of thinking. But while it’s a natural tendency, it’s also a common and harmful issue when conducting a study where your data needs to be accurate. 

Longitudinal studies eliminate these errors from your dataset as much as possible by allowing you to ask participants what they’re experiencing and feeling in the moment. 

For example, you might conduct a study to track industry trends in retail sales around certain times of the year—how do customers feel about your products around the winter holiday shopping season, and do their views change in the middle of summer? This data could help you figure out how to market your products outside of the typical shopping season and increase year-round sales, if it’s accurate. 

If you conduct a cross-sectional survey in the winter and ask participants to remember how they felt about your products or your marketing in the summer, enough time has passed that most people will be subject to recall bias. 

But if you run a longitudinal survey, you can follow up with customers during both the winter and summer seasons while the information is still fresh in their minds. Your data will be more accurate, and your marketing decisions will be more effective at increasing year-round sales. 

Launch your next study

Using longitudinal studies is an essential part of undertaking research in almost any industry. And when you conduct your study using surveys, you can easily check in with a select group of customers, prospects, or employees over time to track changes and stay on top of trends.

Launch your next brand tracking, industry tracking, or other longitudinal survey with Momentive and make your business and marketing decisions with confidence even in the face of swiftly changing attitudes and opinions.

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