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Let’s Ask About Sex: Methodological Merits of the Sealed Envelope Technique in Face-to-Face Interviews

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Devianz und Subkulturen

Part of the book series: Kriminalität und Gesellschaft ((KRIMI))

  • This research was conducted within the projects “Asking Sensitive Questions: Possibilities and Limits of Randomized Response and Other Techniques in Different Survey Modes”, and “Sensitive Questions and Social Desirability: Theory and Methods”, both supported by the German Research Foundation DFG (Priority Program SPP 1292, Grant PR 237/6-1 and Grant WO 2242/1-1).


When it comes to deviant behavior and other sensitive topics, respondents in surveys tend either to refuse answering such sensitive questions or to tailor their answers in a socially desirable direction. This occurs by underreporting on negatively connoted behaviors or attitudes and by overreporting on positively connoted ones (be it deliberately or undeliberate). Thus, prevalence estimates of deviant traits are biased. Moreover, if the tendency to misreport is related to influencing factors of the deviant behavior or attitude under investigation, the correlations are biased as well.

In order to tackle the problems of nonresponse and misreporting to sensitive questions, survey methodology has come up with several special questioning techniques which mostly aim at anonymizing the interview situation and in doing so, to impose less burden on respondents when answering sensitive questions. Among the oldest proposed techniques is the sealed envelope technique (SET) for face-to-face interviews: Respondents are asked to fill out the “sensitive part” of the interview on a self-administered ballot and to seal it in a secret envelope that the interviewer does not open personally.

The aim of our paper is to investigate whether SET has methodological advantages as compared to classic direct questioning (DQ). The data stem from a “sensitive topic survey” among University students in the City of Mainz (Germany, n = 578). The sensitive questions selected for this evaluation pertain to sexual experiences and behavior.

Results show that—compared to direct questions—the sealed envelope technique has some advantages: It reduces misreporting of sensitive behavior; in particular, it helps certain subgroups (e.g. religious people) to overcome subjective barriers in answering sensitive questions accurately; it diminishes item nonresponse; and it lowers subjective feelings of uneasiness of interviewers and respondents when it comes to sensitive issues. The general conclusion is that the sealed envelope technique seems to be a helpful tool in gathering less biased data about sensitive behavior.

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  • 19 May 2020

    Die ursprüngliche digitale Version dieses Werkes wurde zu früh publiziert und wird durch die vorliegende korrigierte Version ersetzt.


  1. 1.

    With respect to social desirability bias, rational choice theory focuses on three determinants of this type of misreporting (Stocké 2007b): 1) respondents’ social desirability (SD) beliefs, i.e. their perceptions of which answer is socially expected, 2) respondents’ need for social approval, and 3) respondents’ feeling of privacy in the interview situation.

  2. 2.

    A third restriction imposed by the registration office was that the students selected were born between May and October. The interviewers did not know about this restriction and asked for the month (and year) of birth in their interviews. This enabled a check of interviewer reliability. Only three interviewers reported birth months outside the May-October range. The field work of these three interviewers was checked thoroughly, but without confirmation of serious cheating.

  3. 3.

    Wording/framing techniques did not make much difference to direct questioning in general; the randomized response procedure used in our survey proved to deliver inconsistent and implausible results (for descriptive findings, see Preisendörfer 2008).

  4. 4.

    Each of the 47 interviewers had an interviewer number. The randomization procedure used this number to determine which type of interview (direct/indirect) an interviewer had to conduct. This assignment of interviewers to questionnaire versions includes the risk to confound interviewer attributes and treatment (direct/indirect), but the randomization should control for this.

  5. 5.

    For example, questions on whether respondents live in a regular partnership or what they consider important for living in a partnership (“love”, “fun”, “freedom”, etc.).

  6. 6.

    From further inspection of the two cases it is difficult to tell whether the reported 100 sex partners are plausible values, misreporting, or a coding error.

  7. 7.

    Confined to those living in a partnership, the mean of coital frequency in the last four weeks goes up to 8, and this corresponds with values obtained from other studies of coital frequency in partnership relations (e.g., Jasso 1985).

  8. 8.

    Within research on social desirability, empirical studies have shown that often there is no consensus regarding which answer to a behavioral or attitudinal question is socially expected, i.e. corresponds to normative expectations (Stocké 2007a, b; Stocké and Hunkler 2007). Based on this finding of heterogeneous “SD beliefs,” it is only a short step to the assumption that SET effects vary for different subgroups of the population.

  9. 9.

    This finding clearly contradicts other empirical studies having found that men report more sexual partners than women (Smith 1992; Tourangeau et al. 1997; Liljeros et al. 2001). We may speculate that our special sample of German university students could be responsible for this result. A widespread hypothesis about sex reporting is that men have a tendency towards overreporting whereas women have a tendency towards underreporting (Tourangeau et al. 1997, p. 355; Krumpal et al. 2018). However, in a recent study, Krumpal et al. (2018) do not find a clear pattern of gender-specific over- and underreporting of lifetime sexual partners, too.

  10. 10.

    We also checked for interaction effects between the respondent’s and interviewer’s gender. We did not find any significant interaction effects with the exception of masturbation: If the interviewer is female and in SET mode only, the negative effect for female respondents is less pronounced as compared to a male interviewer.

  11. 11.

    Note that the questions concerning one-night stands, sexual infidelity and homosexual contacts are formulated with the frame “ever engaged in.” Such a frame is normally less threatening than the frame “currently engaged in.” Moreover, these questions are simple yes/no questions as opposed to the other questions which ask—in a more demanding manner—for numbers and frequencies.

  12. 12.

    With respect to sex questions, Tourangeau et al. (1997), for example, have demonstrated that self-administered questions (SAQs) produce higher levels of reporting. See, for example, Tourangeau and Yan (2007); Wolter (2012, pp. 57–61) for literature reviews regarding the effects of self-administration (and other survey modes) on response behavior.


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Wolter, F., Preisendörfer, P. (2020). Let’s Ask About Sex: Methodological Merits of the Sealed Envelope Technique in Face-to-Face Interviews. In: Krumpal, I., Berger, R. (eds) Devianz und Subkulturen. Kriminalität und Gesellschaft. Springer VS, Wiesbaden.

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