Why the right survey method depends on the target population
Researchers planning a survey in São Tomé and Príncipe often face a practical choice: should an interviewer visit respondents using CAPI, call them using CATI, or invite them to complete CAWI online? The right answer depends on the eligible population, not on a fashionable technology. São Tomé and Santo António provide two contrasting settings for illustrating these trade-offs: the principal urban centre on São Tomé island and the main town on Príncipe island. The comparison can guide a two-city plan, but it must not be presented as evidence for every community in the country.
Choose the survey mode by answering the coverage question first: who belongs to the target population and what realistic chance does each eligible person have of being reached? A household survey, a beneficiary tracking exercise and an online customer poll have different frames. Begin with a table linking each required indicator to its target group, sample source, privacy needs and validation standard. Only then estimate unit costs and interview duration. A lower price per completed interview is not a saving if the cheaper method excludes the intended respondents.
CAPI: when in-person digital interviewing is strongest
CAPI works when observation and face-to-face selection are central to the design. Enumerators can follow preselected area segments, locate dwellings, display consent statements and show visual materials that are awkward by telephone. Digital logic limits some manual entry errors, but it cannot prove that the correct respondent was selected or that the interviewer was neutral. GPS points and duration checks are supplementary quality signals, never substitutes for a transparent sample. Device security, safe routing and interviewer training must be budgeted from the beginning.
CATI: when interviewer-led telephone surveys fit
A telephone survey can be effective when the target group can be contacted lawfully and predictably, but it should never begin with an unchecked list. Clean contact records, verify respondent eligibility and define the appropriate time for calling. Provide a concise purpose statement and respect refusal. Telephone questionnaires generally need shorter sentences and smaller answer lists than face-to-face forms. The reporting should separate dialled numbers, answered calls, screened contacts, eligible contacts and completed interviews. Without that disposition history, high completion totals can conceal selection bias.
CAWI: when self-completed online surveys are credible
CAWI is attractive because responses flow directly into a dataset and participants can answer privately at a convenient time. However, digital access varies by age, resources, geography and user familiarity. The survey must be designed primarily for mobile screens where that reflects the audience, with simple navigation and response options. Verify the panel or invitation list, block duplicate participation where feasible and check unusual answer patterns without collecting unnecessary personal data. Findings should be described as applying to the recruited online population when broader coverage cannot be established.
Use the administrative research geography of São Tomé and Príncipe
A location frame in São Tomé and Príncipe should use the relevant geographic structures, such as districts and the autonomous region of Príncipe, rather than importing another country’s local government labels. The frame should distinguish where people live, work and access services from the administrative boundary used for supervision. A district or municipality may help organise field assignments without supplying a complete list of eligible respondents. Verify any boundaries and contact sources with field teams before sampling. These decisions affect who can enter the CAPI sample, which calling lists may be credible for CATI, and whether a CAWI panel covers the intended area. Island geography can make both travel routes and the reach of phone or online frames highly uneven. Sample designs should explicitly distinguish island populations and avoid interpreting two centres as a national cross-section.
Build a defensible sample before selecting devices
Sampling is not a technical appendix: it determines whether a result means anything outside the completed interviews. For CAPI, check area lists, selected dwellings or facilities and within-household respondent rules. For CATI, inspect how numbers were obtained and whether shared phones or invalid records change eligibility. For CAWI, document recruitment invitations, verification and self-selection. Allocate samples according to the inference required, not an identical quota copied from another project. A comparison of two selected cities remains a two-city result unless a broader probability frame is deliberately added.
Applying CAPI, CATI and CAWI in São Tomé
In São Tomé, the local research environment includes the principal urban centre on São Tomé island. A household livelihood or service-access survey might use mapped clusters and CAPI where the team must visit selected addresses, verify assets or record in-person observations. A CATI follow-up could be considered when respondents have willingly provided functioning numbers, while CAWI may suit a separately defined digitally reachable subgroup. These methods must not be substituted casually: each can select a different type of participant. Pilot questions and contact procedures within selected neighbourhoods before calculating the city estimate.
Applying CAPI, CATI and CAWI in Santo António
In Santo António, the team should independently assess who can be recruited and how, taking account of its character as the main town on Príncipe island. Check whether the listed households or users can be visited safely, whether sufficient valid numbers exist and whether online recruitment would exclude relevant communities. If a mode used in São Tomé proves weak here, an adapted design may be justified, but preserve core indicator definitions. Note that two selected centres do not represent São Tomé and Príncipe as a whole; a claim about the entire country would require a wider sampling strategy.
Adapt questionnaire design for each survey mode
Pilot all three modes against the same learning objective. Ask whether participants understand the consent language, whether the requested recall period is feasible and whether sensitive questions can be answered privately. In CAPI, observe interviewer explanations. In CATI, listen for complicated sentences and call fatigue. In CAWI, observe navigation, loading and abandonment points. Reconcile corrections through a controlled instrument register. A successful pilot demonstrates comprehension and workable sampling, not merely that the programmed questionnaire saves responses.
Test the actual languages respondents use
Interviewers and respondents may prefer different languages across the same city. Plan local screening, consent and questionnaire testing in Portuguese, Forro and other locally relevant creoles, choosing versions based on the actual target group rather than a single presumed national language. CATI needs phrases that are easy to understand by voice and not overly long. CAWI needs instructions that remain clear without an interviewer. CAPI can support spoken clarification, but staff must not explain questions inconsistently. A short glossary, cognitive pilot and version-control register help maintain concept equivalence across languages and modes.
Plan access, travel and connectivity around local conditions
For this country, a practical design consideration is that the two-island design needs distinct transport and translation assumptions. Evaluate whether this affects road access for CAPI, call completion for CATI, or digital coverage and completion for CAWI. Conduct a reconnaissance and pilot in each selected centre. Estimate realistic interview duration, interviewer workloads, callback needs, connectivity and secure data transfer rather than applying an unchanged budget from another country. If teams change modes mid-project, document why and test whether the change affects the measured indicators.
Know when mixing modes improves coverage
A mixed-mode design can be sensible if the modes cover complementary groups by design. For example, CAPI might reach selected households lacking reliable numbers, while CATI covers an existing beneficiary list; CAWI might be reserved for digitally active professionals. Do not recruit convenient respondents from all three channels and call the total nationally representative. Agree how invitations will be tracked to prevent duplicates, which questions may be mode-sensitive, and whether final results will be shown separately or weighted into a defined combined population. The reasons for mode allocation should appear in the methods section before results are interpreted.
Apply mode-specific data quality checks
A useful control room turns warnings into action. Unusually rapid CAPI completes should trigger a case review, not pressure on interviewers to be slower. CATI call records should reveal unproductive attempts and concentration in particular contact times. CAWI reports should show drop-off, device compatibility and suspicious repeats. In each case, a supervisor should be responsible for investigating and documenting the outcome. Feedback to the field team must correct processes while avoiding shortcuts that distort sample selection or respondent autonomy.
Treat consent and privacy as part of research design
Consent, privacy and safety cannot be delegated to the survey platform. A CAPI interviewer should explain the study in language the respondent understands, provide a private setting and collect only the identifiers necessary for the research. CATI requires sensitivity to who else can hear a call and whether the recipient is free to continue. CAWI needs a clear information screen, purposeful data collection and an easy way to stop. Recording, location tracking, contact-list use and data transfers should follow the rules and permissions applicable to the specific assignment.
Analyse mode effects and report coverage limits
Once data arrive, keep mode and recruitment information in the dataset. Examine completion patterns, item nonresponse and demographic composition separately for CAPI, CATI and CAWI. A mode difference may reflect sample composition, question presentation or both. Do not treat every difference as a finding about respondent attitudes. Use weights only where their derivation is credible and explain any residual coverage gaps. A transparent report tells readers how each group was reached, what estimates represent and where interpretation should remain cautious.
An illustrative survey decision for São Tomé and Príncipe
Imagine a research organisation assessing São Tomé and Príncipe residents’ experience of health or education services. One component may require direct observation of a facility, which favours CAPI; another may involve checking in with beneficiaries already enrolled on a verified contact list, which can favour CATI. A third component may solicit structured feedback from employees or registered online users, which may fit CAWI. The question is not which technology wins overall, but which population and evidence requirement each technology can legitimately serve. For São Tomé and Santo António, set different logistics assumptions while applying the same rules for respondent eligibility and data quality.
A method-selection decision for São Tomé and Príncipe should explicitly compare: population coverage; sample-frame defensibility; language and questionnaire fit; respondent privacy; requirements for direct observation; connectivity and travel constraints; consent and data protection; interviewer verification; nonresponse; and cost per valid, usable interview. A simple choice table can rank CAPI, CATI and CAWI against the particular study, rather than using a universal hierarchy. A cheap method that systematically misses core respondents is usually a poor value, while an expensive method with no extra evidence benefit may also be hard to justify.
What a credible survey report should contain
The study protocol should specify sampling units, city boundaries, contact or visit schedules, translated questionnaires, mode-specific recruitment procedures, quality checks, data storage and the rules for excluding or replacing cases. Reporting should provide separate denominator and nonresponse information for São Tomé and Santo António when they are compared, with a clear limitation on inference beyond those populations. Good survey research gives programme managers and business leaders evidence they can use, plus enough operational detail to understand its strengths and gaps. It does not disguise coverage problems behind a high response count.
How Surveysphere Africa can support
Surveysphere Africa supports the design and delivery of CAPI, CATI, CAWI and carefully planned mixed-mode studies. For projects in São Tomé and Príncipe, including São Tomé and Santo António, the team can help define a credible sample, localise instruments, supervise fieldwork, verify data quality and explain which populations the evidence represents. The best method is the one that reaches the intended respondents and yields defensible decisions.
Related guidance
For the continent-wide view, read our guide to CAPI, CATI and CAWI.
Our services for research in São Tomé and Príncipe
We run research across African markets. Start with these services for work in São Tomé and Príncipe:
- Outsourced fieldwork in São Tomé and Príncipe: CAPI, CATI and CAWI data collection with live quality control.
- Market and consumer research in São Tomé and Príncipe: Market-entry, consumer and retail research.
We also offer: Monitoring, evaluation and learning, Social and development research, Public health research, Policy, economic and institutional research, Data analytics and insights visualisation.
