---
watermark: ORIRO
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name: sci-research-methods
provider: ORIRO.ai
copyright: Copyright (c) 2026 ORIRO.ai
description: >






  Research methods — study design, sampling, data collection, literature review, academic writing, and research ethics.
  Sources: OpenStax textbooks (CC-BY), Khan Academy, MIT OCW, NOAA, IPCC reports.
---

# Research Methods

## Research design hierarchy

**Systematic reviews/meta-analyses:** Synthesize all studies on a question. Highest level of evidence for most questions.
**Randomized controlled trials:** Experimental design with randomization. High internal validity.
**Cohort studies:** Follow people over time. Can establish temporal sequence.
**Case-control studies:** Compare exposed vs. unexposed, looking backward.
**Cross-sectional:** Snapshot. Good for prevalence; cannot establish causation.
**Case reports/expert opinion:** Lowest evidence. Hypothesis-generating.

## Sampling

**Probability sampling (scientific):** Every member of population has known probability of selection.
Simple random: Every member equal probability. Gold standard for generalization.
Stratified: Divide into groups, sample from each. Ensures representation.
Cluster: Sample groups, then individuals within groups. More practical for large populations.
Systematic: Every nth person from a list.

**Non-probability sampling (practical):**
Convenience: Whoever is available. High bias. Limits generalizability.
Purposive: Deliberately select specific types. Qualitative research.
Snowball: Participants recruit other participants. Social networks, hidden populations.

**Sample size determination:** Based on effect size, desired power (0.80), and significance level (0.05). Use G\*Power or similar calculators.

## Literature review

**Systematic vs. narrative:**
Systematic: Pre-specified search strategy, inclusion/exclusion criteria, documented. Reproducible.
Narrative: Selectively reviews literature based on author's knowledge. Prone to bias.

**Search strategy:**
Databases: PubMed (biomedicine), PsycINFO (psychology), Scopus, Web of Science, JSTOR, Google Scholar.
Boolean operators: AND (narrow), OR (expand), NOT (exclude).
MeSH terms: Medical Subject Headings — controlled vocabulary for PubMed.

**Critical appraisal:** Don't accept published studies uncritically.
Check: Is the study design appropriate for the question? Was randomization done correctly? Was blinding appropriate? Was the sample size adequate? Were confounders addressed? Do conclusions match the data?

**PICO search strategy:** Population + Intervention + Comparison + Outcome → generates focused search terms.

## Academic writing

**IMRaD structure:** Introduction, Methods, Results, and Discussion.
Introduction: What is known? What is the gap? What is the research question?
Methods: Detailed enough to replicate. Study design, participants, measurements, analysis plan.
Results: What was found. Data, statistics, tables, figures. No interpretation here.
Discussion: What does it mean? Compare to prior literature. Limitations. Implications.

**Writing principles:**
Precision: Use exact terms. Avoid weasel words (may, perhaps, seems).
Economy: One idea per sentence. Delete unnecessary words.
Active vs. passive: "We conducted..." vs "The study was conducted..." Active is clearer.
Citation management: Zotero (free), Mendeley, EndnoteRelevant.

## Research ethics

**Informed consent:** Participants must understand: what the study involves, risks and benefits, right to withdraw, how data will be used.
**Confidentiality vs. anonymity:** Confidentiality = identifiable but protected; Anonymity = cannot be identified.
**IRB/Ethics review:** Required for research involving human subjects.
**Research misconduct:** Fabrication (making up data), Falsification (manipulating data), Plagiarism (taking credit for others' work). Career-ending and potentially criminal.
**Publication bias:** Positive results more likely to be published. Contributes to replication crisis. Pre-registration helps.

Sources: OpenStax Research Methods (CC-BY), Cochrane handbook (free, cochrane.org),
Creswell Research Design (principles), APA Publication Manual (principles)