Instruments & methods for data collection

Pasquale Schifino

Data collection is a central component of scientific research.

Without reliable data, hypotheses cannot be tested and informed decisions cannot be made.

Depending on the subject of investigation, the research design, and the available resources, different methods and instruments are used.

A basic distinction is made between quantitative and qualitative methods, as well as between primary data collection (data collected by the researcher) and secondary data analysis (use of existing data).

This article systematically presents the most important methods and instruments for data collection, explains their special features, and points out their advantages and disadvantages.

🎯 The most important summarized:

Without systematic data collection, there is no basis for valid analyses and targeted measures in companies.

Primary data is collected anew (e.g., through surveys), while secondary data uses existing information—the choice should be made carefully depending on the objective.

Surveys, observations, tests, or interviews—depending on the target group and the question being asked, certain methods are more suitable than others.

Tools such as online surveys, personal interviews, or automated feedback systems must be used methodically and professionally in order to achieve valid results.

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Table of contents

1. Quantitative methods

2. Qualitative methods

3. Secondary analysis & document analysis

4. Mixed methods & triangulation

5. Conclusion

6. More on the topic of data collection

Quantitative methods

Quantitative methods are based on the measurement and numerical representation of phenomena.

The aim is to make generalizable statements.

1. Method: Standardized survey

The standardized survey is one of the most common methods of data collection.

It is carried out via:

Online questionnaires (e.g., easyfeedback)
Telephone interviews
Face-to-face interviews with questionnaires
Postal surveys

Typical instruments:

Likert scales (e.g., from “strongly disagree” to “strongly agree”)
Multiple-choice questions
Rating scales

Advantages:

Comparability of responses
Low distortion by interviewers (in the case of self-administration)
Easy evaluation (e.g., with SPSS or Excel)

Disadvantages:

Limited depth
Risk of standard responses or socially desirable responses
Low response rate for written surveys

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2. Method: Tests and psychometric procedures

These methods assess skills, characteristics, or attitudes using standardized procedures:

Intelligence tests

Personality tests (e.g., Big Five, MBTI)
Performance tests (e.g., concentration, arithmetic ability)
Attitude scales

Advantages:

Objectivity, reliability, and validity can be measured
Wide range of comparison options (standard values)

Disadvantages:

Cultural biases are possible
Test anxiety can influence results

3. Method: Structured observation

Structured observation is based on a clearly defined observation scheme.

Examples:

Customer behavior in retail stores
Classroom observations in schools
Behavior analysis in animals

Advantages:

Direct recording of behavior
Nonverbal aspects can also be observed

Disadvantages:

Reactivity (behavior changes when observed)
Limited to what can be observed

4. Method: Experiments

Experiments examine the causal relationship between variables under controlled conditions.

Types:

Laboratory experiments
Field experiments
Online experiments

Advantages:

High internal validity
Control over confounding factors

Disadvantages:

Low ecological validity in laboratory experiments
Time-consuming preparation and ethical issues

Qualitative methods

Qualitative methods are suitable for researching complex, subjective, or social phenomena.

The data is usually linguistic (text, audio) and is evaluated interpretively.

1. Method: Qualitative interviews

Forms:

Guided interviews (semi-structured)
Narrative interviews (open, story-oriented)
Problem-centered interviews

Advantages:

Deep insight into subjective perspectives
Flexible application

Disadvantages:

Time-consuming evaluation (e.g., transcription)
Interviewer bias possible

2. Method: Focus groups / group discussions

A moderated discussion of 5–10 people on a specific topic.

Areas of application:

Product development
Social research
Health communication

Advantages:

Interactive opinion formation visible
Different perspectives simultaneously

Disadvantages:

Dominance of individual participants
Time-consuming moderation

3. Method: Participatory observation

The researcher is actively involved in the events, e.g., in the context of field research.

Examples:

Ethnographic studies
Social space analyses

Advantages:

Deep understanding of social processes
Access to hard-to-reach groups

Disadvantages:

Subjectivity of the observer
Ethical issues with covert participation

4. Method: Qualitative content analysis

Systematic analysis of text material (e.g., interviews, newspaper articles, social media posts) according to defined categories.

Examples:

Mayring’s qualitative content analysis
Grounded theory

Advantages:

Structured evaluation of complex content
Theory development possible

Disadvantages:

Interpretation is subjective
Time-consuming

Secondary analysis & document analysis

This involves drawing on existing data.

Sources:

Official statistics (e.g., from Destatis)
Scientific databases
Company reports
Social media analyses
Newspapers and magazines

Advantages:

Quickly available
Cost-effective

Disadvantages:

Little control over survey methods
Data may be outdated or inaccurate

Mixed methods & triangulation

A combination of quantitative and qualitative methods.

Example:

Quantitative survey plus qualitative interviews for more in-depth analysis

Advantages:

Complementary strengths of the methods
Greater significance

Disadvantages:

Very time-consuming
High demands on methodological knowledge

Conclusion

The variety of methods and instruments available for data collection allows researchers to obtain as accurate a picture as possible of their subjects.

While quantitative methods provide objective, statistically evaluable data, qualitative methods enable a deep understanding of individual perspectives and social processes.

The choice of the appropriate method should always be tailored to the research question and take practical conditions into account.

In many cases, a combination of different methods—i.e., a mixed-methods approach—offers the greatest gain in knowledge.

Regardless of the method, however, it is crucial that the data collection is carried out systematically, transparently, and in an ethically responsible manner.