When searching databases, these are some of the keywords you can use to identify empirical research:
Analysis
Case Studies
Empirical Research
Evaluation Research
Experiment/s
Field Studies
Field Work
Focus Groups
Interviews
Measure or measurement(s)
Methodology
Online Surveys
Original study
Outcomes
Participatory Observation
Qualitative Research
Quantitative Research
Research study
Sample size
Statistical Analysis
Statistics
Surveys Mixed Methods Research
Usage