# **2. Literature Review**

The question of the interviewers’ effects on the respondent’s answers has been addressed extensively in the social science literature, and the findings vary widely depending on the variable under discussion and the context of the survey. A common mechanism by which interviewers can introduce bias is through an action on the part of the interviewer that deviates from survey protocols, either intentional or unintentional, verbal or non-verbal. Though training is designed to prevent this behavior, interviewers often deviate (Billiet & Loosevelt, 1988; Fowler & Mangione, 1990). In particular, Cannell, Miller & Oksenberg (1981) note a tendency to elaborate and paraphrase difficult questions. The questions in the Timor-Leste study would be particularly vulnerable to this as they use an unfamiliar forced-choice format and address slightly abstract topics. These questions were also both subjective and sensitive, which the literature has found to be more vulnerable to interviewer effects, though there are some exceptions. See Cotter, Cohen & Coulter (1982), Davis (1997), Davis, Couper, Janz, Cadwell & Resnicow (2010), Groves (1989), Samples et al (2014), Schaeffer (1980), and Schnell & Kreuter (2005) for further discussion.

In addition to explicit actions, it is also possible to introduce bias even while following protocols if the respondent alters their answer based on the physical characteristics of the interviewer, such as age, race, and gender. While findings again vary with context, most literature find significant impacts, particularly with race and gender. See Collins & Butler (1983), Davis (1997), Ellison, McFarland & Krause (2011), Finkel, Geterbock & Borg (1991), Freeman & Butler (1976), Galla, Frisone, Jeffrey & Gaer (1981), Hatchett & Schuman (1975), Krysan & Cooper (2003), Rhodes (1994), Singer, Frankel & Glassman (1983) for examples. In addition, these effects may be amplified for sensitive issues, such as gender and sexual practices (Tu & Liao, 2007; Johnson & Moore, 1993; Lueptow, Moser & Pendleton, 1990; Johnson & DeLamater, 1976; Galla, et al, 1981). The results from the literature are more mixed with regard to interaction effects. For example, while Huddy et al (1997) found an average increase of five percentage points on a dichotomous question for female-to-female interviews, and similar findings are recorded by Lueptow et al (1990) and Landis, Sullivan & Sheley (1973), mixed results are found by Ballou (1990), Johnson & DeLamater (1976) and Catania et al (1996). Related to age, Wallace, Kohout & Colsher (1992) found that older respondents were more comfortable with older interviewers.

The literature is more limited on the impact of the interviewer’s beliefs on the respondent’s answers. In one of the earliest examples of interviewer effects in the literature, Rice (1929) found that an interviewer’s personal politics, in this case socialism versus prohibition, led to wide differences the main cause of destitution cited by respondents. More recently Hermann (1983, discussed in Schnell & Kreuter, 2005) found “interviewer effects were small if the item was unimportant to the interviewer and that they were large if the item was unimportant to the respondent.” There are fewer examples of studies conducted outside of the United States. Phung, Hardeweg, Praneetvatakul & Waibel (2013) found significantly higher errors based on interviewer 3