How to Write the Population and Sample for a Doctoral Dissertation

How to Write the Population and Sample for a Doctoral Dissertation

The population and sample section of a doctoral dissertation explains who will participate in the study, how participants are selected, and why the selected group is appropriate for answering the research questions. This section is typically included in Chapter 3 (Methodology) and is essential for establishing the credibility and rigor of the research design.

A strong population and sample section clearly identifies:

• The target population

• The sample size

• Sampling procedures

• Inclusion and exclusion criteria

• Rationale for participant selection

In simple terms, this section answers: “Who is being studied, and how were they selected?”

What Is the Population in a Dissertation?

The population refers to the entire group of individuals, organizations, or cases that the researcher wants to study.

Examples of populations:

• Undergraduate students at a university

• K–12 teachers in public schools

• Healthcare workers in hospitals

• Online doctoral students

• Parents of children with autism

The population should align directly with:

• The research problem

• Research questions

• Methodology

What Is a Sample in a Dissertation?

The sample is the smaller group selected from the population to participate in the study.

Because researchers usually cannot study an entire population, they select a sample that represents the population of interest.

Example:

• Population: All doctoral students enrolled in online programs

• Sample: 20 online doctoral students from one university

Why the Population and Sample Section Matters

This section demonstrates:

• Research credibility

• Appropriate participant selection

• Alignment with methodology

• Ethical and practical feasibility

Dissertation committees expect researchers to justify:

• Why the sample was chosen

• How participants were recruited

• Whether the sample is appropriate for the study design

Where Is the Population and Sample Section Located?

This section is typically found in:

• Chapter 3: Methodology

It often appears under headings such as:

• Population

• Sample

• Participants

• Sampling Procedures

• Sampling Strategy

Step-by-Step: How to Write the Population and Sample Section

Step 1: Identify the Target Population

Clearly define the broader group relevant to the study.

Include:

• Who the participants are

• Relevant characteristics

• Geographic or institutional context

Example:

The target population for this study consisted of K–12 public school teachers employed in urban school districts in the United States.

Step 2: Describe the Sample

Explain the smaller group selected from the population.

Include:

• Estimated sample size

• Participant characteristics

• Relevant demographics

Example:

The sample included 25 middle school teachers with at least three years of online teaching experience.

Step 3: Explain the Sampling Method

Describe how participants were selected.

Common Sampling Methods

Quantitative Sampling Methods

Random Sampling

Participants selected randomly from the population.

Stratified Sampling

Population divided into subgroups before sampling.

Convenience Sampling

Participants selected based on accessibility.

Qualitative Sampling Methods

Purposive Sampling

Participants selected because they have direct experience with the phenomenon.

Criterion Sampling

Participants must meet specific criteria.

Snowball Sampling

Participants recruit additional participants.

Example:

Purposive sampling was used to recruit participants with experience teaching online courses during the COVID-19 pandemic.

Step 4: Justify the Sample Size

Explain why the sample size is appropriate.

Quantitative Studies

Sample size may be based on:

• Statistical power analysis

• Previous research

• Expected effect size

Qualitative Studies

Sample size may depend on:

• Data saturation

• Depth of participant experience

• Methodological recommendations

Example (Qualitative):

The sample size of 12 participants was considered sufficient to achieve thematic saturation.

Example (Quantitative):

A sample size of 150 participants was selected to provide adequate statistical power for regression analysis.

Step 5: Define Inclusion Criteria

Inclusion criteria explain who is eligible to participate.

Examples:

• Adults over age 18

• Full-time teachers

• Students enrolled in doctoral programs

• Participants with at least one year of experience

Example:

Participants were required to have completed at least one fully online doctoral course.

Step 6: Define Exclusion Criteria

Exclusion criteria explain who cannot participate.

Examples:

• Individuals under age 18

• Participants without relevant experience

• Incomplete survey responses

Example:

Participants without online teaching experience were excluded from the study.

Step 7: Describe Recruitment Procedures

Explain how participants will be contacted or recruited.

Common recruitment methods:

• Email invitations

• Social media recruitment

• Institutional announcements

• Professional organizations

• Classroom or workplace recruitment

Example:

Participants were recruited through university email announcements distributed to doctoral students.

Step 8: Address Ethical Considerations

Discuss participant protections such as:

• Informed consent

• Confidentiality

• Voluntary participation

• Data security

Mention:

• Institutional Review Board (IRB) approval if applicable

Example:

Participation was voluntary, and all responses were kept confidential in accordance with IRB guidelines.

Population and Sample Examples by Research Type

Example for a Quantitative Study

The target population consisted of undergraduate nursing students enrolled in online programs at public universities in the United States. A convenience sample of 200 students was recruited through institutional email invitations. Participants were required to be at least 18 years old and enrolled full-time during the data collection period.

Example for a Qualitative Study

The population for this phenomenological study included doctoral students who experienced academic burnout during online learning. Purposive sampling was used to recruit 12 participants who met the inclusion criteria of being currently enrolled in a doctoral program and reporting burnout-related experiences.

Common Mistakes in the Population and Sample Section

Avoid:

• Failing to clearly define the population

• Using vague participant descriptions

• Not justifying sample size

• Choosing a sampling method inconsistent with methodology

• Omitting inclusion or exclusion criteria

• Ignoring ethical recruitment procedures

Tips for Writing a Strong Population and Sample Section

• Align participants with research questions

• Use precise participant descriptions

• Clearly explain sampling procedures

• Justify sample size logically

• Address ethical considerations thoroughly

• Use terminology consistent with your methodology

Quantitative vs. Qualitative Population and Sample Differences

Quantitative Research	Qualitative Research
Larger sample sizes	Smaller sample sizes
Focus on generalizability	Focus on depth of experience
Random or probability sampling	Purposive or criterion sampling
Statistical power important	Data saturation important

Final Thoughts on How to Write the Population and Sample for a Doctoral Dissertation

The population and sample section is a critical component of a doctoral dissertation because it explains who is being studied and how participants were selected. A strong section demonstrates methodological rigor, ethical planning, and alignment between the research problem, questions, and participant selection process.

Whether conducting qualitative, quantitative, or mixed methods research, carefully describing the population, sample, sampling strategy, and recruitment procedures strengthens the credibility and trustworthiness of the study.

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