research-methodology

Research Methodology — Research Methodology Design Framework

A specialized skill that enhances the methodology-expert agent's research design capabilities.

Target Agent

• methodology-expert — Research design, sample, instrument, and analysis method selection

Research Design Type Selection Matrix

Research Question -> Design Type Mapping

Research Question Type	Suitable Design	Data Type
"What is ~?" (exploratory)	Qualitative (grounded theory, phenomenology)	Interviews, observation
"What is the relationship between ~?" (correlational)	Quantitative (survey, secondary data)	Numerical data
"Does ~ affect ~?" (causal)	Experimental / quasi-experimental	Experimental data
"How is ~ experienced?" (phenomenological)	Phenomenological research	In-depth interviews
"How has ~ developed?" (process)	Grounded theory, case study	Multiple sources
"For an integrated understanding of ~?"	Mixed methods	Quantitative + qualitative

Quantitative Research Designs

Design Type	Characteristics	Internal Validity	Application
True experiment (RCT)	Random assignment + control group	High	Medicine, educational interventions
Quasi-experiment	Non-random + control/comparison group	Medium	Field education research
Non-experimental (survey)	Observational, correlational	Low	Exploratory, descriptive
Longitudinal	Tracks changes over time	Medium	Developmental, panel studies
Cross-sectional	Single-point measurement	Low	Status assessment

Qualitative Research Designs

Design Type	Purpose	Data Collection	Participant Count
Phenomenology	Explore the essence of experience	In-depth interviews	5-25
Grounded theory	Generate theory	Interviews, observation	20-30
Case study	Understand phenomena in context	Multiple sources	1-10 cases
Ethnography	Understand cultural context	Participant observation	Extended period
Narrative	Personal experience narrative	Life history interviews	1-5

Sample Design

Quantitative Sample Size Calculation

n = (Z^2 x p x (1-p)) / e^2

Z = Confidence level (95% -> 1.96, 99% -> 2.576)
p = Expected proportion (if unknown, use 0.5)
e = Margin of error (typically +/-5% = 0.05)

Population	95% conf, +/-5%	95% conf, +/-3%
100	80	92
500	217	341
1,000	278	516
10,000	370	964
100,000+	384	1,067

Minimum Sample for Regression Analysis

N >= 50 + 8 x (number of independent variables)  (Tabachnick & Fidell)
or
N >= 15 x (number of independent variables)  (Stevens)

Measurement Instrument Validity and Reliability

Validity

Type	Verification Method	Criterion
Content validity	Expert panel review (CVI)	CVI >= 0.80
Construct validity	Factor analysis (EFA/CFA)	Factor loading >= 0.40
Convergent validity	AVE	AVE >= 0.50
Discriminant validity	sqrt(AVE) > correlation	Fornell-Larcker criterion
Criterion validity	Correlation with external criterion	r >= 0.40

Reliability

Type	Verification Method	Criterion
Internal consistency	Cronbach's alpha	alpha >= 0.70
Composite reliability	CR (SEM)	CR >= 0.70
Test-retest	Repeated measurement with same instrument	r >= 0.70
Inter-rater	Cohen's Kappa	kappa >= 0.60

Analysis Method Selection Guide

Research Purpose -> Analysis Method

Research Purpose	Independent Variable	Dependent Variable	Analysis Method
Difference test (2 groups)	Categorical	Continuous	t-test
Difference test (3+ groups)	Categorical	Continuous	ANOVA
Relationship analysis	Continuous	Continuous	Correlation analysis
Impact analysis	Continuous/Categorical	Continuous	Regression analysis
Structural relationships	Latent variables	Latent variables	SEM
Group classification	Continuous/Categorical	Categorical	Logistic regression
Categorical relationship	Categorical	Categorical	Chi-square test

Alternatives When Assumptions Are Violated

Assumption	Alternative
Normality	Mann-Whitney, Kruskal-Wallis
Equal variance	Welch's t-test, Games-Howell
Independence	Repeated measures ANOVA, paired t-test
Linearity	Nonlinear regression, variable transformation