Research Design Guide
Research design is the structural blueprint of your study. This guide walks through the main design types, the basics of sampling, and how to think about validity and reliability, in plain language.
Research Design vs. Methodology
It's worth being clear on this distinction from the outset: methodology is the broader philosophical reasoning behind your approach, while research design is the practical structure that follows — your sample, your instruments, and the specific way your study is put together. Two students can share a methodology and still need very different designs.
Common Research Design Types
| Design | Typically Used When... |
|---|---|
| Cross-sectional | You need a snapshot of a population at one point in time |
| Longitudinal | You're tracking change over time — less common in shorter dissertations |
| Experimental | You're testing cause-and-effect relationships between variables |
| Case study | You're exploring one organisation, event, or context in depth |
| Correlational | You're examining relationships between variables without manipulating them |
Sampling Basics
Sampling decisions shape what you can and can't claim from your findings, so they deserve careful thought early on.
Probability sampling gives every member of your population a known chance of being selected, supporting broader generalisation. Non-probability sampling — such as convenience or purposive sampling — is more common in student research and entirely valid, provided its limitations are acknowledged honestly.
- Define your population clearly before deciding how to sample from it
- Choose inclusion and exclusion criteria you can defend if questioned
- Justify your sample size against your planned analysis, not an arbitrary round number
- Be realistic about who you can actually access within your timeframe
Validity, Reliability & Trustworthiness
Quantitative and qualitative research use different vocabulary for the same underlying concern: can readers trust your findings? Quantitative designs typically address internal validity, external validity, and reliability directly. Qualitative designs more often address credibility, transferability, dependability, and confirmability — evidenced through concrete steps like piloting an instrument, triangulating data sources, or keeping a reflexive journal.
Key Takeaways
- Research design is the practical structure that follows from your broader methodology
- Non-probability sampling is common and valid in student research when its limitations are acknowledged
- Validity and reliability (quantitative) and trustworthiness (qualitative) both need to be evidenced with specific, concrete steps
Research Design Guide FAQs
This depends on whether your research questions are about a snapshot or about change over time — longitudinal designs are powerful but often impractical within a typical dissertation timeframe.
Yes, it's widely used and accepted in student research, provided you're transparent about its limitations, such as reduced generalisability, in your methodology chapter.
Validity refers to whether you're actually measuring what you intend to measure; reliability refers to whether your measurement is consistent if repeated.