How Does Interview Quality Affect the Number of Participants Needed in Qualitative Research?

Can Better Interviews Reduce the Number of Participants a Qualitative Study Needs?

You have completed ten qualitative interviews. Some participants provided detailed accounts, concrete examples, and reflections on difficult experiences. Others answered most questions in one or two sentences.

Although all ten interviews count toward your sample, they have not contributed the same amount or quality of information.

Should you recruit more participants, improve your interview technique, or reconsider whether the available data are sufficient?

Interview quality is an important consideration in qualitative sample-size planning because the usefulness of an interview depends not only on its existence or duration but also on how well it supports the intended analysis.

Richer Interviews May Reduce Recruitment Needs, but Quality Cannot Replace Necessary Variation

How Interview Quality Influences Information Richness and Sample Adequacy

What Does Interview Quality Mean in Qualitative Research?

Interview quality concerns how effectively an interview generates material relevant to the research question and suitable for the intended qualitative analysis.

A high-quality interview may include detailed descriptions, contextual explanations, concrete examples, reflections on experiences, and opportunities to explore contradictions.

However, quality is not equivalent to the length of the transcript or the number of words spoken.

A relatively short interview may provide highly relevant information for a focused question, while a lengthy interview may contain substantial material unrelated to the research aim.

Quality should therefore be assessed in relation to the analytical purpose rather than through duration or word count alone.

How Does Interview Quality Relate to Information Power?

Malterud, Siersma, and Guassora (2016) identify quality of dialogue as one of five dimensions of information power.

The framework proposes that a sample containing highly relevant and rich information may require fewer participants than one providing less informative material.

Dialogue quality interacts with the research aim, sample specificity, established theory, and analysis strategy.

For example, detailed interviews with experienced online course designers may provide substantial information for a focused study of assessment-development decisions.

However, rich interviews from one participant group cannot automatically replace perspectives required for a comparative study.

The information power framework therefore treats dialogue quality as one contributor to adequacy, not a universal substitute for participant numbers.

What Makes an Interview Analytically Rich?

An analytically rich interview provides material that can support interpretation beyond general statements or brief opinions.

For example, a teacher might say that generative AI makes assessment design easier. That statement identifies a perception but provides limited information about the underlying experience.

A richer account might describe the assessment task, how AI was used, what difficulties arose, how the teacher evaluated the output, and why particular revisions were made.

Such detail allows the researcher to examine processes, contextual conditions, and possible tensions within the experience.

Richness also includes contradictions and uncertainty. Participants do not need to provide coherent or favorable narratives for their accounts to be analytically useful.

Why Does Interview Question Design Matter?

Interview questions shape the opportunities participants have to describe their experiences.

Questions that invite concrete accounts may produce more useful information than questions asking only for agreement or general opinions.

These examples illustrate how question design can improve opportunities for detailed responses. They are not universally appropriate interview questions and should be adapted to the methodology and research aim.

How Does Probing Improve Interview Quality?

Probing involves asking follow-up questions that encourage clarification, elaboration, or reflection.

For example, after a participant describes difficulty implementing an online assessment, the interviewer might ask what made the situation difficult, how the participant responded, and whether the experience changed subsequent practice.

Effective probing can reveal meanings and contextual details that remain hidden in an initial response.

However, probing should not become pressure to produce a particular answer.

Leading questions, repeated demands for confirmation, or interviewer assumptions can distort the material rather than enrich it.

Can Too Much Probing Reduce Interview Quality?

Yes. Excessive probing can interrupt participants' narratives, create discomfort, or encourage responses shaped by the interviewer's expectations.

For example, repeatedly asking whether a teacher experienced ethical concerns may imply that such concerns are expected, even when they were not central to the participant's experience.

Good probing follows the participant's account while remaining attentive to the research question.

The interviewer should allow participants to challenge assumptions, decline questions, or identify experiences the researcher did not anticipate.

Interview quality involves responsive judgment, not simply asking more follow-up questions.

Why Does Rapport Matter?

Rapport can help participants feel sufficiently comfortable to describe experiences openly and in detail.

This may be particularly important when discussing professional uncertainty, institutional conflict, or practices that participants perceive as sensitive.

However, rapport should not be confused with agreement or friendship.

An interviewer who appears to endorse every participant statement may inadvertently discourage critical reflection or alternative perspectives.

Ethical rapport involves respectful engagement, clear expectations, and attention to the participant's autonomy.

How Do Power Relationships Affect Interview Quality?

Power relationships can influence what participants are willing to disclose.

For example, teachers interviewed by someone involved in evaluating their professional performance may hesitate to discuss institutional problems or unsuccessful instructional decisions.

Students interviewed by their own instructor may similarly feel pressure to provide favorable accounts.

These concerns cannot be resolved simply by recruiting more participants.

Researchers should consider interviewer roles, confidentiality arrangements, recruitment procedures, and the possibility of perceived coercion.

Reflexive attention to these conditions can improve the credibility of the data and help explain limitations in what participants disclose.

Does Interviewer Experience Affect Sample Adequacy?

Interviewer experience may influence the ability to ask clear questions, recognize opportunities for probing, manage difficult interactions, and follow unexpected lines of inquiry.

Experienced interviewers may obtain richer material from some participants, but experience alone does not guarantee quality.

A novice interviewer who prepares carefully, practices interviewing, and engages reflexively with the data may conduct effective interviews.

Researchers should evaluate the actual informational contribution of interviews rather than assume that interviewer credentials determine adequacy.

Can Pilot Interviews Improve the Quality of Main Interviews?

Pilot interviews can help identify confusing questions, unsuitable sequencing, excessive interview length, or missed opportunities for elaboration.

They may also reveal whether participants understand the terminology used in the interview schedule.

For example, teachers may interpret "AI-assisted assessment" differently, making it necessary to clarify the intended focus without imposing a restrictive definition.

Pilot interviews can therefore improve the main data collection process.

However, pilot participants should not automatically be included in the final analytical sample. Inclusion depends on whether the pilot data were collected under sufficiently compatible conditions and whether their use is ethically and methodologically justified.

Does Interview Duration Determine Data Quality?

No. Longer interviews may create more opportunities for detailed discussion, but duration is an imperfect indicator of informational value.

A sixty-minute interview can contain extensive repetition or tangential discussion. A thirty-minute interview may provide focused and substantial information about a narrowly defined experience.

Researchers should examine the relevance, specificity, and interpretive usefulness of the material.

Interview duration can be reported as contextual information, but it should not be treated as a direct measure of quality or sample adequacy.

Are Face-to-Face Interviews Always Better Than Online Interviews?

No. Interview mode can influence interaction, but no single mode is universally superior.

Online interviews may improve access to geographically dispersed participants and allow participation from familiar environments.

They can also introduce connectivity problems, reduced access to some nonverbal cues, or privacy concerns.

Face-to-face interviews may facilitate certain forms of interaction but can impose travel burdens or make participants less comfortable discussing sensitive topics.

The appropriate mode depends on the research aim, participant circumstances, ethical considerations, and the kind of interaction required.

Can Written Interviews Provide Rich Qualitative Data?

They can, depending on the research question and participants.

Written responses may allow participants time to reflect and formulate detailed accounts.

However, asynchronous written formats can limit opportunities for immediate clarification and responsive probing.

Researchers should distinguish a structured questionnaire containing short open-ended responses from an extended written interview involving follow-up exchanges.

The adequacy of written material depends on its relevance and analytical richness, not simply the number of respondents.

How Does Interview Quality Affect Data Saturation?

Interview quality can influence how quickly recurring codes or issues become visible.

However, superficial interviews may create an artificial appearance of repetition because participants have not been given opportunities to describe complex experiences.

For example, repeated answers that AI saves time may suggest a recurring code, but further probing might reveal substantial differences in verification work, assessment type, or institutional expectations.

Therefore, data saturation should not be assessed solely by counting repeated short responses.

The researcher must consider whether the material is sufficiently developed for the intended analytical purpose.

Can Rich Interviews Eliminate the Need for More Participants?

Sometimes they may reduce the need for additional recruitment, but they cannot replace information about experiences absent from the sample.

Suppose ten teachers provide detailed accounts of assessment design within one discipline. Their interviews may support an intensive investigation of that context.

However, the same material may be insufficient for a study intending to compare assessment practices across several disciplines.

The specificity and variation of the sample remain important even when interview quality is high.

What If Several Interviews Produce Very Little Information?

Researchers should first examine why the interviews were limited.

Possible explanations include poorly aligned participant selection, unclear questions, insufficient rapport, technical difficulties, or limited participant experience of the phenomenon.

Different causes require different responses.

If participants lack relevant experience, eligibility criteria may need revision. If questions are too general, the interview schedule may need improvement. If participants are reluctant to disclose information, ethical and relational conditions may need attention.

Simply increasing recruitment without addressing the cause may reproduce the same limitations.

Should Poor Interviews Be Excluded From Analysis?

Not automatically. An interview that appears brief or less detailed may still contain relevant information.

Excluding interviews solely because they do not support emerging interpretations can introduce bias.

Researchers should distinguish genuine data-quality problems from accounts that are unexpected, concise, or analytically challenging.

Exclusion decisions should follow defensible methodological criteria and be documented transparently.

Where interviews are retained, their limitations can be considered during interpretation.

Can Follow-Up Interviews Improve Sample Adequacy?

Yes. Follow-up interviews may help clarify ambiguous accounts, explore emerging questions, or develop greater depth without recruiting entirely new participants.

For example, a teacher may initially describe difficulty balancing AI assistance and assessment integrity. A later interview could explore specific decisions and how those decisions changed over time.

However, repeated interviews with the same participants do not necessarily replace the need for additional perspectives.

The decision should depend on whether the main limitation concerns depth within existing cases or missing variation across cases.

How Can Researchers Assess Interview Quality During Data Collection?

Researchers can review transcripts and analytical notes after early interviews.

Useful questions include whether participants provide concrete examples, whether important concepts remain unclear, and whether the material supports the intended analysis.

A structured review may help identify improvements without reducing quality to a numerical score.

This framework is a practical assessment aid rather than a validated interview-quality instrument.

Its purpose is to guide methodological reflection and decisions about whether the current data collection strategy is producing sufficient information.

How Should Interview Quality Influence Recruitment Decisions?

Recruitment decisions should respond to the actual informational needs of the analysis.

If interviews are rich but important participant perspectives remain missing, additional targeted recruitment may be necessary.

If the sample is appropriate but interviews lack detail, improving interviewing or conducting follow-up interviews may be more useful than recruiting indiscriminately.

If the material is both relevant and sufficiently rich for the intended analysis, further recruitment may contribute limited additional value, depending on the methodology.

The decision about when to stop qualitative recruitment should therefore consider interview quality alongside the research aim and analytical adequacy.

How Should Interview Quality Be Reported?

Researchers should describe the interview approach, relevant interviewer preparation, procedures for probing, and any changes made during data collection.

They may also report interview duration, mode, and the use of follow-up interviews when these details help readers understand the data.

However, reporting average interview length does not demonstrate richness by itself.

A stronger account explains how the interviews supported the analytical purpose and how limitations were considered.

Reflexive discussion of interviewer-participant relationships can further clarify the conditions under which the data were produced.

Improving Interview Quality Before Increasing Participant Numbers

The example illustrates that increasing interview quality may improve information power without necessarily increasing participant numbers.

However, changes to the interview schedule should be documented, and the researcher should consider whether differences between early and later interviews affect comparability and interpretation.

Common Misconceptions About Interview Quality and Sample Size

Improve the Information Collected Before Increasing Recruitment Indiscriminately

Assess interview quality during data collection rather than waiting until all interviews have been completed.

Determine whether limitations arise from participant selection, question design, interviewing practices, or missing perspectives.

Better interviews may reduce unnecessary recruitment, but they do not eliminate the need for sufficient relevant participants.

The strongest sample-size justification considers the quality of the information obtained and the scope of the interpretations the researcher intends to develop.

Before Deciding Whether More Qualitative Interviews Are Needed

Frequently Asked Questions About Interview Quality and Sample Size

Interview Quality Influences How Much Information a Sample Provides

How to Cite This Guide

This guide is intended to be read, shared, and used in research, teaching, and academic work. If you draw on its ideas, explanations, or other content, please acknowledge the source by citing the guide. Doing so gives appropriate credit and helps your readers locate the original resource.