How to identify relevant variables from a literature review?

By Riya Jain & Priya Chetty on July 18, 2022

Variables are simply factors that represent properties, qualities, or characteristics of a person, thing, or concept. Any research paper like a thesis or dissertation requires relevant variables to be defined correctly. They can be as simple as demographic characteristics such as age, gender, or income (Marudhar, 2018). Other times they can be more complex like the psychological traits of an individual. Researchers do a thorough literature review to identify these complex variables.

Different types of variables in a research

Variables of any study are of four main types.

Identifying relevant variables in a research
Figure 1: Identifying relevant variables in a research

A dependent variable is a variable that is dependent on the value of another variable. So if anything in the first variable changes then the dependent variable changes too.

‘Weight’ is often dependent on the ‘age’ of an individual. Here, ‘weight’ is the dependent variable.

Marudhar, 2018; USCLibraries, 2017

An independent variable is a variable that is unaffected by other variables of the study. In studies, these variables could be regarded as the factors affecting the key research term.

‘Age’ is not related to ‘gender’, i.e. if a person’s gender changes then his age does not change. Therefore they both are independent variables.

A demographic variable is a variable that represents the basic demographic characteristics of the nature of respondents included in the study. They are neither independent nor dependent. Common demographic variables are age, gender, income, location, profession and marital status.

An extraneous variable is also known as an intervening variable and they make a relationship stronger or weaker.


While assessing how age affects a person’s tolerance to alcohol, weight is an extraneous variable that may or may not actually affect the tolerance.

Categorising relevant variables as dependent and independent variables

Literature review for major studies serves as a major methodological tool to answer research questions. It aims to delve deep into the background of the research topic. For this, researchers study review relevant research papers published in reputable publications.


Xiang et al. (2014) examined the factors influencing project governance in china and determined that aspects like system management, stakeholder management, risk management, integrity management, cost management, and audit management affect the project performance (strategic and operational). Agemb & Oyugi (2017) further explored the critical success factors for project performance and stated that factors like project manager competency, project team competency, rules and procedure compliance, and subcontractor services influence the project performance. Lastly, Ramesh et al. (2018) in their examination of project success derived that human resource management, task management, schedule management, and feasibility study contribute to influencing project performance.

With the empirical review of the literature in the above example, it can be derived that project performance is the dependent variable represented by:

  • project success,
  • strategic performance,
  • and operational performance.

While aspects like:

  • system management,
  • stakeholder management,
  • risk management,
  • integrity management,
  • cost management,
  • audit management,
  • project manager competency,
  • project team competency,
  • rules and procedure compliance,
  • subcontractor services,
  • human resource management,
  • task management,
  • schedule management and,
  • feasibility study

are possible independent variables.


To find out an answer to the research question of how many Indonesian consumers liked to consume nicotine and why:

  1. First, do a background check of how many Indonesians are actually consuming nicotine.
  2. Procure 20 good studies from reputed publications in the last 10 years to make a literature review and understand all the possible reasons people consume nicotine.
  3. Identify the independent variables such as ‘stress’, ‘easy availability, or ‘peer pressure which cause everyone to consume nicotine.
  4. Lastly, find out the hidden (extraneous) factors which indirectly affect Indonesians to consume nicotine, such as ‘alcohol is not easily available.

In this case, the dependent variable is the consumption of nicotine and the independent variables are stress, easy availability and peer pressure.

Presenting the identified relevant variables in the conceptual framework

In the literature review, researchers commonly use a diagram known as a conceptual framework to map out the linkage between the variables. A conceptual framework is a visual or written representation of the possible or expected relationships between variables (Swaen, 2021). A conceptual framework helps to identify the correct way to test the relationship between two variables. Thus, the presentation of variables in the conceptual framework should be to state the mix of variables and their linkage based on existing studies (Regoniel, 2015).

From the above example of the empirical review of literature, the conceptual framework can be presented as:

Independent variables

  • System management
  • Stakeholder management
  • Risk management
  • Cost management
  • Audit management
  • Competency
  • Subcontractor services
  • Human resource management
  • Task management
  • Schedule management

Dependent variable

Project performance

Dependent variable components

  • Project success
  • Strategic performance
  • Operational performance

While identifying relevant variables in a literature review, it is important that:

  • The variables should be consistent with the goal.
  • They should be measurable and replicable. Avoid making ‘feeling’ a variable.
  • The stated variables should have been widely used in recent years or at least defined in recent terms.
  • The variable should be within the stated study design.
  • Variables identified should be valid, reliable, prevalent, and common in the community.
  • Should be mentioned or determined based on literature review.
  • The variables should not be out of scope, very rare, or time-consuming.
ZamenPub, 2019


Priya is the co-founder and Managing Partner of Project Guru, a research and analytics firm based in Gurgaon. She is responsible for the human resource planning and operations functions. Her expertise in analytics has been used in a number of service-based industries like education and financial services.

Her foundational educational is from St. Xaviers High School (Mumbai). She also holds MBA degree in Marketing and Finance from the Indian Institute of Planning and Management, Delhi (2008).

Some of the notable projects she has worked on include:

  • Using systems thinking to improve sustainability in operations: A study carried out in Malaysia in partnership with Universiti Kuala Lumpur.
  • Assessing customer satisfaction with in-house doctors of Jiva Ayurveda (a project executed for the company)
  • Predicting the potential impact of green hydrogen microgirds (A project executed for the Government of South Africa)

She is a key contributor to the in-house research platform Knowledge Tank.

She currently holds over 300 citations from her contributions to the platform.

She has also been a guest speaker at various institutes such as JIMS (Delhi), BPIT (Delhi), and SVU (Tirupati).


I am a master's in Economics from Amity University. Having a keen interest in Econometrics and data analysis, I was a part of the Innovation Project of Daulat Ram College, Delhi University. My core expertise and interest are in environment-related issues. Apart from academics, I love music and exploring new places.


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