Infographic: How to write the rationale of your research
A rationale answers one question: Why does this study need to exist? It is not a literature review nor an introduction. It is a focused argument that justifies your research by showing a gap, a problem, or an unresolved question that your study will address.
The Core Structure of a Rationale
Every strong rationale moves through four logical steps:
- Establish what is known: Summarize the existing evidence in 2–3 sentences. Be selective. Only include what directly sets up your gap.
- Identify what is unknown or problematic: State the gap, inconsistency, limitation, or unanswered question in the literature. This is the pivot point.
- Explain why the gap matters: Connect the gap to a real-world consequence, a theoretical problem, or a practical need. Without this, the reader has no reason to care.
- State what your study will do about it: One or two sentences describing your study’s purpose as a direct response to the gap.
The Gap-Rationale Matrix
Use this framework to identify which type of rationale fits your study:
| Gap Type | What It Looks Like | Example Rationale Opening |
| Knowledge gap | Topic has never been studied | “No study has examined X in population Y.” |
| Methodological gap | Prior studies used flawed or limited methods | “Previous research relied solely on self-report; no study has used objective measures.” |
| Population gap | Existing evidence excludes your group | “Most trials enrolled only adults; the pediatric population remains unstudied.” |
| Conflicting evidence | Studies disagree | “Findings on X are inconsistent, ranging from significant benefit to no effect.” |
| Replication gap | Findings haven’t been confirmed elsewhere | “This effect has only been demonstrated in one laboratory setting.” |
| Contextual gap | Evidence exists elsewhere but not in your context | “While validated in Western settings, this intervention has not been tested in low-income countries.” |
Identify which gap type applies to your study before you write a single sentence.
Sentence-Level Formula
The rationale can be written in as few as four sentences using this template:
- Known: “Studies consistently show that [X].”
- Unknown: “However, [specific gap: what has not been studied, who has been excluded, what remains inconsistent].”
- Consequence: “This limits [clinical practice / theoretical understanding / policy / patient outcomes] because [reason].”
- Your response: “The present study therefore aims to [your objective] in order to [what it will contribute].”
Common Mistakes in Writing Your Rationale and How to Fix Them
| Mistake | Why It Weakens the Rationale | Fix |
| Starting with a very broad background | Buries the gap under unnecessary context | Begin with the gap, not the history of the field |
| Stating the gap without explaining its consequences | Reader doesn’t understand why it matters | Always follow the gap with “This matters because…” |
| Vague gap statements (“little is known about X”) | Doesn’t tell the reader what specifically is unknown | Be precise: name the population, outcome, or method that is missing |
| Listing multiple unrelated gaps | Dilutes the argument | Focus on one gap that your study directly addresses |
| Confusing rationale with objectives | Objectives describe what you’ll do; rationale explains why it must be done | Keep them separate: rationale first, objectives second |
| Overclaiming the gap | Implies no prior work exists when it does | Use hedged language: “few studies,” “no study in this population,” “limited by…” |
How Long Should a Rationale Be?
- In a journal article: 1–3 paragraphs, embedded at the end of the introduction
- In a grant proposal: 1–2 pages, often a standalone section
- In a thesis: 3–5 paragraphs, with more explicit reference to the literature
Length is secondary to completeness. A rationale that covers all four steps in 150 words is stronger than one that rambles for 500 words without clearly stating the gap.
How Is the Rationale Different from the Introduction?
The introduction provides context. The rationale provides justification. The introduction tells the reader what the field looks like; the rationale tells the reader why your study must exist within that field.
- The introduction may span several paragraphs covering background, definitions, and prior work.
- The rationale is always the final movement of the introduction: the logical conclusion that the background has been building toward.
- If someone reads only your rationale, they should understand the gap and why your study addresses it: without needing the rest of the introduction.
What If My Study Is Exploratory and There Is No Clear Gap?
Exploratory studies still need a rationale: the gap is simply epistemic rather than empirical.
- State that the phenomenon is understudied or poorly characterized
- Explain what practical or theoretical decisions depend on understanding it better
- Frame your study as generating hypotheses or a framework for future confirmatory work
Example: “The mechanisms by which X influences Y in community settings remain poorly characterized. Without a clearer understanding of these pathways, designing targeted interventions is premature. This study therefore takes an exploratory approach to map the key variables and generate hypotheses for future trials.”
How Do I Know If My Rationale Is Strong Enough?
Run your rationale through this checklist before submission:
- The gap is stated in one specific sentence
- The gap is supported by at least one citation showing what has been done (to define the boundary of knowledge)
- The consequence of the gap is explicit, not implied
- The study’s response to the gap is directly stated
- The rationale does not claim a gap that your own literature review contradicts
- A non-specialist could read the rationale and understand why the study is necessary
If you can check every box, your rationale is ready.
In this infographic, we have listed how you may write the rationale of your research:
Please feel free to download this infographic and send it to your colleagues or post on social media.
This article was originally published on January 6, 2023, and updated on March 27, 2026.
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