03 · What You Need to Know
How to Determine Whether an Existing Instrument Is Suitable for Another Population
What Does Population Adaptation Mean?
Population adaptation involves evaluating and, where necessary, modifying an existing measurement instrument for respondents whose relevant characteristics differ from those of the population in which it was originally developed or evaluated.
These differences may concern age, educational level, professional role, language proficiency, disability-related access needs, experience with the measured phenomenon, or other characteristics relevant to the response process.
For example, an academic self-efficacy questionnaire developed for postgraduate students may contain tasks involving scholarly publication, independent research design, or advanced statistical analysis.
Those tasks may be inappropriate for students who have not yet encountered them.
Population adaptation requires determining whether the original measurement task remains meaningful and whether the intended construct can be represented appropriately among the new respondents.
Is Using an Instrument With Another Population Always Considered Adaptation?
Not necessarily. Researchers should distinguish extending the use of an unchanged instrument from modifying its content or administration.
An instrument may be administered unchanged to a new population when the construct, items, and response procedures remain appropriate.
However, using the same instrument does not eliminate the need to examine whether existing validity evidence applies to the new population.
For example, a questionnaire developed with students at one university might be appropriate for students at another institution without textual changes.
Whether additional evaluation is necessary depends on relevant differences between the populations, the available evidence, and the intended interpretation.
Thus, population transfer and instrument modification are related but distinct decisions.
Why Does the Original Validation Population Matter?
Measurement evidence is obtained under particular conditions involving specific respondents, tasks, scoring procedures, and intended interpretations.
An instrument's performance in one population does not establish that every other population will interpret its items or generate scores in the same way.
For example, a measure of instructional confidence developed among experienced teachers may include activities that preservice teachers understand theoretically but have never performed independently.
The resulting responses might reflect anticipated confidence rather than confidence grounded in professional experience.
The Standards for Educational and Psychological Testing emphasize that validity concerns the evidence supporting particular interpretations and uses of scores.
Researchers should therefore evaluate the relevance of the original evidence rather than treating validation as a permanent characteristic of the questionnaire.
Which Population Differences Are Most Important?
Not every demographic difference has the same measurement implications.
The important differences are those that could influence the construct, item relevance, comprehension, response processes, or scoring.
| Population Difference |
Possible Measurement Concern |
Potential Evaluation |
| Educational level |
Items assume unfamiliar academic tasks or terminology |
Content review and cognitive interviews |
| Professional experience |
Respondents have different opportunities to perform behaviors |
Construct and item applicability review |
| Age or developmental stage |
Questions impose unsuitable comprehension or recall demands |
Age-appropriate response-process evaluation |
| Language proficiency |
Terminology or response labels are interpreted differently |
Comprehension testing and language review |
| Accessibility needs |
Presentation or response controls create barriers |
Accessibility and usability testing |
| Experience with the phenomenon |
Items assume activities respondents have not encountered |
Target-population consultation |
| Institutional environment |
Opportunities and procedures differ across settings |
Contextual relevance and comparability evaluation |
These are potential concerns rather than assumptions about individuals. Researchers should investigate whether the differences actually affect the intended measurement.
Must the Construct Mean the Same Thing in Both Populations?
When researchers intend to retain the original construct interpretation, conceptual continuity is essential.
For example, academic self-efficacy concerns perceived capability to perform relevant academic tasks. However, the tasks that meaningfully represent that capability may differ between beginning and advanced students.
Changing the tasks may preserve the broader theoretical construct while altering the particular domain represented by the score.
Researchers should therefore distinguish continuity at the theoretical level from equivalence of the operational measure.
If the intended construct changes substantially, the work may be better described as redevelopment rather than straightforward adaptation.
The importance of clearly defining the construct before instrument development also applies when transferring existing measures to new populations.
How Do You Determine Whether the Original Items Are Relevant?
Review each item against the construct definition and the experiences available to the intended respondents.
An item may be understandable but inapplicable. For example, undergraduate students may understand a question about submitting journal manuscripts even if most have never attempted publication.
Another item may describe an activity that occurs in both populations but has a different practical meaning.
Researchers should consider whether the item measures the intended attribute, whether respondents have a meaningful basis for answering, and whether essential construct content remains adequately represented.
A content matrix can document these judgments systematically.
Should You Adapt Wording to Match the New Population?
Wording changes may be appropriate when the original terminology is unfamiliar, misleading, or contextually unsuitable.
For example, an item referring to "professional development activities" may require clarification when administered to preservice teachers whose relevant activities occur within coursework or supervised practice.
However, replacing professional activities with student activities may change the behavior being assessed.
The revised item should therefore be evaluated for conceptual continuity and respondent comprehension.
The broader principles for modifying an existing research questionnaire apply whenever population adaptation requires textual or procedural changes.
Can You Remove Items That Do Not Apply to the New Population?
Potentially, but deletion may alter content coverage and the meaning of total or subscale scores.
For example, removing all items about classroom management from a teacher competence questionnaire may make it easier to administer to preservice teachers who have limited classroom experience.
However, the resulting instrument may no longer represent the same breadth of teaching competence.
Researchers should examine whether adaptation, an existing subscale, or another instrument would be preferable.
The consequences of removing items from an established questionnaire depend on what those items contribute, not merely their number.
Can You Add Population-Specific Items?
Yes, when they address relevant content that is inadequately represented by the original instrument.
However, adding questions to the survey is different from incorporating them into the original scale score.
For example, a researcher might administer an established academic engagement questionnaire alongside supplementary questions about asynchronous learning activities.
If the additional items are scored separately, the original scale may remain intact.
If they contribute to the original total score, the instrument's measurement configuration changes and requires appropriate evaluation.
The distinction is examined further in adding items to an existing questionnaire.
Should the Response Options Be Changed for the New Population?
Response categories should be comprehensible and suitable for the judgment requested.
However, reducing a seven-category scale to five categories or replacing agreement ratings with frequency categories may change the response process.
Researchers should not assume that a population requires simpler categories merely because its members are younger or have different educational experiences.
Instead, evaluate whether respondents can distinguish the categories meaningfully.
Any consequential change should be documented and examined using appropriate evidence.
The specific issue of changing response options without revalidation is relevant when adaptation affects the scale format.
What Role Should Experts Play in Population Adaptation?
Experts can evaluate whether the construct remains relevant, whether the proposed content represents its intended dimensions, and whether changes preserve conceptual meaning.
A suitable review group may include subject specialists, measurement specialists, and individuals familiar with the new population.
For example, adapting a questionnaire from practicing teachers to preservice teachers may benefit from expertise in teacher education and educational measurement.
However, expert approval alone does not establish that respondents understand the revised items as intended.
Expert judgments should be combined with appropriate evidence from the target population.
Why Should Members of the New Population Review the Instrument?
Target-population review helps identify unfamiliar terminology, irrelevant assumptions, and differences in how respondents understand questions.
For example, an instrument may ask students how confidently they can "evaluate scholarly evidence." Beginning students may interpret this as checking whether an article appears professional, while advanced students may consider methodological quality and evidentiary strength.
Both groups can answer the question, but their responses may represent different judgments.
Appropriate target-population review and cognitive interviewing can investigate these differences before main data collection.
Does the Original Instrument's Reliability Evidence Transfer?
Not automatically. Reliability estimates depend on the scores, population, measurement conditions, and statistical model.
For example, an instrument may distinguish experienced professionals effectively but show restricted score variation among novices because many items concern advanced tasks.
Alternatively, items may function differently when respondents have little direct experience with the activities being assessed.
Researchers should estimate relevant reliability properties in the new population when necessary and interpret them in relation to the intended use.
A favorable Cronbach's alpha does not independently establish that the construct has been represented appropriately.
Can the Factor Structure Change Across Populations?
Yes. Relationships among questionnaire items may differ across populations.
For example, planning and monitoring may appear closely related among beginning learners but more distinguishable among experienced students.
Such differences may reflect substantive characteristics, measurement problems, or sampling variability.
When total or subscale scores depend on a particular dimensional structure, researchers should examine whether the proposed model remains appropriate.
However, a different factor pattern does not automatically prove that the construct itself is different.
Interpretation requires theoretical and empirical consideration.
What Is Measurement Invariance?
Measurement invariance concerns whether a measurement model operates sufficiently comparably across groups to support particular score comparisons.
For example, researchers may wish to compare academic self-efficacy between undergraduate and postgraduate students.
If items function differently across the groups, observed score differences may not represent differences in the intended construct alone.
Depending on the model and comparison, researchers may investigate structural, loading, threshold, or intercept equivalence.
Different levels of invariance support different interpretations, and their necessity depends on the intended analysis.
Measurement invariance is therefore not a single universal test that every adaptation must pass in exactly the same way.
What Is Differential Item Functioning?
Differential item functioning, or DIF, occurs when respondents from different groups with the same standing on the relevant latent attribute have different probabilities of endorsing or answering an item in a particular way.
For example, an item about confidence in presenting research at conferences may function differently between students with and without opportunities to attend conferences, even after accounting for the intended attribute.
DIF analysis can help identify items requiring investigation.
However, statistical evidence of DIF does not automatically establish unfairness or explain its cause.
Researchers should examine the item content, population experiences, and intended score interpretation before deciding whether modification or removal is warranted.
Must Measurement Invariance Be Established Before Every Population Adaptation?
No. The need depends on whether the study intends to compare groups, interpret common score units, or make other inferences requiring equivalence.
If an instrument is used only within a new population, relevant content, response-process, structural, and reliability evidence may be more immediately important.
If the study compares the original and new populations, measurement comparability becomes a central concern.
Even then, the appropriate method depends on the instrument and measurement model.
Researchers should avoid applying factor-analytic invariance procedures mechanically to measures for which their assumptions are unsuitable.
Can the Same Instrument Be Used for Children and Adults?
Potentially, but developmental differences may affect item relevance, comprehension, recall, and response selection.
For example, children and adults may understand abstract frequency labels or hypothetical judgments differently.
Some items may also describe experiences unavailable to younger respondents.
Adaptation should be based on evidence about the intended age group rather than an assumption that simplifying vocabulary is sufficient.
Where age-related differences are consequential, additional content and response-process evaluation may be necessary.
Can an Instrument Be Adapted From Professionals to Students?
Yes, but the researcher should distinguish actual competence, perceived competence, and anticipated capability.
For example, a questionnaire asking practicing teachers how effectively they manage classroom disruptions may not measure the same attribute when administered to preservice teachers who have not yet taught independently.
Students may answer based on expectations rather than observed professional experience.
Rewording the item to ask about anticipated confidence may create a legitimate new measurement task, but it should not be assumed equivalent to the original professional practice measure.
The appropriate decision depends on the research question and intended construct.
Can an Instrument Be Adapted for a Population With Different Accessibility Needs?
Yes. Accessible administration may require alternative presentation formats, assistive technology compatibility, or other accommodations.
However, adaptations should preserve the intended construct as far as possible.
For example, changing a visually presented assessment into an audio format may be appropriate when visual decoding is not part of the construct.
If the construct itself concerns visual interpretation, the implications are different.
Researchers should distinguish removing construct-irrelevant barriers from changing the ability or experience being assessed.
Accessibility should be considered during instrument design rather than treated as an afterthought.
Does Population Adaptation Always Require Translation?
No. Populations may differ substantially while sharing the same language.
For example, a questionnaire developed for postgraduate researchers may require adaptation for undergraduate students without any language change.
Conversely, populations may share similar educational characteristics but use different languages.
Translation and population adaptation can overlap, but they address different questions.
When language changes are necessary, formal translation and cultural adaptation procedures may also be required.
How Much Additional Validity Evidence Is Needed?
The necessary evidence depends on the extent of population differences, instrument modifications, and intended use.
For a closely comparable population, existing evidence combined with targeted comprehension and reliability evaluation may be sufficient for some purposes.
For a substantially different population, broader investigation of content, response processes, dimensionality, and score comparability may be necessary.
When the instrument provides a primary outcome or supports consequential individual decisions, unresolved measurement weaknesses deserve particular attention.
The issue of when instrument adaptation requires new validity evidence should be resolved according to the intended interpretation rather than a fixed checklist.
Should the Adapted Instrument Be Called a New Instrument?
Not automatically. An adapted version may retain an identifiable relationship to the original instrument through its construct definition, items, and scoring.
However, extensive changes to content, dimensions, and score interpretation may constitute substantial redevelopment.
There is no universal percentage of changed items that determines the distinction.
Researchers should identify the original source, describe the adapted version accurately, and avoid implying that the two versions have identical measurement properties without evidence.
What Permissions Are Needed?
Permission requirements depend on the instrument's copyright, licensing terms, contractual conditions, and applicable law.
Some instruments permit adaptation under specified conditions, while others require authorization.
Researchers should examine the original documentation before reproducing, translating, or modifying protected content.
Legal authorization and methodological appropriateness are separate matters. Permission to adapt an instrument does not establish that the adapted scores are valid.
How Should Population Adaptation Be Reported?
Reports should identify the original instrument, its development population, the intended new population, and the rationale for adaptation.
Describe all consequential changes to wording, items, response options, administration, and scoring.
Explain which original evidence remains relevant and what additional evidence was obtained.
If comparisons across populations are intended, report how measurement comparability was investigated and acknowledge unresolved limitations.
Maintain an item-level record as part of documenting instrument modifications.
Watch Out
Do not assume that an instrument is appropriate for a new population simply because respondents can answer its questions or because it produced a high reliability coefficient in the original population. Item relevance, construct meaning, response processes, and scoring may differ in ways that affect the intended conclusions.
