Do Interviewers' Health Beliefs and Habits Modify Responses to Sensitive Questions? A Study using Data Collected from Pregnant Women by Means of Computer-assisted Telephone Interviews
Anne-Marie Nybo Andersen1,2 and
Jørn Olsen3
1 Department of Epidemiology Research, The Danish Epidemiology Science Centre, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark.
2 Department of Social Medicine, University of Copenhagen, 3 Blegdamsvej, DK-2200 Copenhagen N, Denmark.
3 The Danish Epidemiology Science Centre, University of Aarhus, 6 Vennelyst Boulevard, DK-8000 Aarhus C, Denmark.
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ABSTRACT
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If interviewers' personal habits or attitudes influence respondents' answers to given questions, this may lead to bias, which should be taken into consideration when analyzing data. The authors examined a potential interviewer effect in a study of pregnant women in which exposure data were obtained through computer-assisted telephone interviews. The authors compared interviewer characteristics for 34 interviewers with the responses they obtained in 12,910 interviews carried out for the Danish National Birth Cohort Study. Response data on smoking and alcohol consumption in the first trimester of pregnancy were collected during the time period October 1, 1997February 1, 1999. Overall, the authors found little evidence to suggest that interviewers' personal habits or attitudes toward smoking and alcohol consumption during pregnancy had consequences for the responses they obtained; neither did the interviewers' education, age, or parity correlate with the answers they obtained. In these data gathered through computer-assisted telephone interviews, interviewer effects arising from variations in interviewers' health beliefs and personal habits were found to be negligible. Thorough training of the interviewers and continuous supervision may have contributed to this finding.
data collection; effect modifiers (epidemiology); epidemiologic methods; interviews; pregnancy; telephone
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INTRODUCTION
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An observer interferes with the object of observation and makes a unique recording that probably cannot be replicated down to its final detail. However, the aim in epidemiology is to make objective recordings which can be replicated within reasonable limits.
It is known that face-to-face interviewing involves a substantial risk of producing interviewer effectsthat is, responses that depend partly on how the interviewer looks, poses the questions, and expresses his or her attitude in body language and wording (1
). Self-administered questionnaires are generally believed to be less vulnerable to influences on response patterns (2
); however, even in studies using questionnaires, the aim of the study, the appearance of the questionnaire, the introductory letter, and the research group may all have an impact on response (3
).
Telephone interviewing falls between these two data collection methods. Computer-assisted telephone interviewing has become the method of choice in many studies, because it permits use of a highly branched questionnaire. Further-more, telephone interviews often have high response rates and few missing data, and they are usually less expensive than personal interviews, though more expensive than self-administered questionnaires (4
).
An interviewer effect would be expected to be smaller in telephone interviews than in personal interviews, since only the interviewer's voice and the phrasing of the questions cannot be standardized. On the other hand, the absence of face-to-face contact with the interviewer might make it difficult for the respondent to find the confidence needed to give honest answers to personal questions (5
).
It is important for epidemiologists to evaluate the quality of the data collection methods they apply (6
). If an interviewer effect is present in computer-assisted telephone interviews, researchers must take this into consideration when designing a study or analyzing results.
The Danish National Birth Cohort Study is an ongoing project with the aim of establishing a cohort of 100,000 women, recruited in the first trimester of pregnancy, and their offspring. Information on exposures incurred during pregnancy is collected primarily by means of telephone interviews. We use computer-assisted telephone interviewing and a highly structured questionnaire for these telephone interviews. As part of our quality control, we ask all interviewers to provide data on their own attitudes and habits concerning specific lifestyle factors.
The aim of this particular study was to assess possible interviewer bias arising from the interviewers' own habits and their attitudes toward a woman's lifestyle during pregnancy. For this purpose, we compared the interviewers' demographic characteristics, personal smoking and alcohol-drinking habits, and personal attitudes toward drinking and smoking during pregnancy with the responses they obtained on alcohol and smoking from pregnant women in the Danish National Birth Cohort Study.
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MATERIALS AND METHODS
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We used response data from the first of four interviews carried out with participants in the Danish National Birth Cohort Study during the period October 1, 1997February 1, 1999. For the interviewers, we used data from a self-administered questionnaire filled in when they started their employment with the study.
The telephone interviews were carried out in one centralized setting by trained personnel employed by a commercial call center. All interviewers were women of reproductive age. The interviewers had to pass a 2-day training course arranged by us.
The interviewers were asked to complete a questionnaire on their own education, personal reproductive experience, lifestyle habits (smoking and alcohol consumption), and attitudes toward smoking and alcohol drinking during pregnancy. The interviewers were informed about the purpose of the study and were guaranteed full confidentiality. The completed questionnaires were available only to us. A consecutive sample of 40 interviewers completed the questionnaire.
Attitudes toward smoking and alcohol drinking during pregnancy were assessed by asking the interviewers whether they agreed or disagreed with the following three statements: 1) "It is more important for a pregnant woman to stay happy than to stop smoking." 2) "I think that one should, first of all, show concern for the unborn child while pregnant." 3) "One should quit drinking alcoholic beverages while pregnant." On the basis of five fixed answer categories ranging from full agreement to complete disagreement, the interviewers' attitudes were classified arbitrarily as restrictive, neutral, or liberal. This classification was made before the data were analyzed. We constructed the classification to make "restrictive" indicative of at least two maximally restrictive answers or three modified somewhat restrictive statements and "liberal" indicative of, at maximum, one restrictive statement (table 1). Information on alcohol consumption was categorized into three strata according to average weekly alcohol intake: up to two drinks per week, 2
to seven drinks per week, and more than seven drinks per week. Information on education was dichotomized according to the requirements for higher education in Denmark.
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TABLE 1. System for scoring interviewers' attitudes toward specific factors related to a woman's lifestyle during pregnancy, Danish National Birth Cohort Study, 19971999
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Data from the first interview with the pregnant participants, which most often was carried out during gestational weeks 1216, were used for this validation study. A total of 19,216 of these interviews were consecutively carried out between October 1, 1997, and February 1, 1999. Of these, 13,205 were conducted by interviewers who had completed a questionnaire. Six of the 40 interviewers carried out fewer than 100 interviews and were excluded from the study according to the protocol, leaving 12,910 interviews for this analysis. Outcome measures in the study were the respondents' answers to sensitive questions, defined as questions on smoking and alcohol consumption during pregnancy.
Respondents were categorized as smokers or nonsmokers, and their daily consumption of tobacco was categorized into four strata. The women were asked about their average weekly intake of beer, wine, and spirits during pregnancy and before pregnancy, respectively. They were also asked about binge drinking (consumption of five or more drinks on one occasion) during pregnancy. The women's total weekly alcohol consumption was grouped into four strata.
Respondents were assigned to interviewers consecutively. The pregnant women were asked to indicate a preferred day and time for the interview when they signed the informed consent form, and interviews were listed according to preferred time. The interviewers were instructed to carry out the interviews scheduled for a particular time period when on duty, without taking into consideration any characteristics of the respondents. Some interviewers preferred to work during normal working hours; others interviewed women primarily during the evenings and on weekends. Since interviewers' preferred working schedules, as well as participants' preferred times for interview, were expected to be associated with lifestyle factors, we adjusted for potential selection bias by stratifying analyses according to the time of the interview (daytime on a workday vs. weekend or evening).
Data were analyzed using contingency tables (PROC FREQ in SAS (SAS Institute, Inc., Cary, North Carolina)). Differences were evaluated by chi-squared statistics. Permission was obtained from the Danish Data Protection Board before initiation of this study.
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RESULTS
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The interviewers were all women, and their characteristics are shown in table 2. Although all interviewers were of reproductive age, most were nulliparous. Most of the interviewers had started pursuing a higher education or were planning to do so.
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TABLE 2. Characteristics of interviewers according to the number of interviews completed for the study, Danish National Birth Cohort Study, 19971999
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Answers to questions on smoking and alcohol consumption during pregnancy are shown in table 3. The proportion of missing answers was less than 1 percent for smoking and less than 0.5 percent for alcohol intake.
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TABLE 3. Respondents' reported answers to sensitive questions on smoking and alcohol drinking during pregnancy, Danish National Birth Cohort Study, 19971999
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We found no association between the interviewers' alcohol-drinking habits and the answers they obtained about respondents' alcohol intakes during pregnancy (table 4). Responses did not vary by the interviewers' age, parity, educational level, vocational training, or smoking status or by their attitudes toward smoking and drinking during pregnancy.
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TABLE 4. Respondents' reported alcohol intake during pregnancy (%) according to interviewer characteristics, Danish National Birth Cohort Study, 19971999
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Table 5 shows the distributions of answers on smoking according to the interviewers' alcohol intake, smoking habits, and attitudes toward specific lifestyle factors in pregnancy. No significant associations were seen. Similarly, the interviewers' education, vocational training, age, and parity were not related to the pregnant women's reporting of smoking or alcohol drinking during pregnancy (data not shown).
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TABLE 5. Respondents' reported smoking during pregnancy (%) according to interviewer characteristics, Danish National Birth Cohort Study, 19971999
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Analysis of possible selection bias related to the time of interview showed that interviews performed during regular working hours were significantly more likely to be carried out by interviewers who smoked, had a high consumption of alcohol, and had a liberal attitude toward lifestyle in pregnancy (table 6). Consequently, all analyses were stratified according to whether or not the interview was completed during regular working hours. The stratification revealed a weak association between interviewers' alcohol consumption and respondents' reporting of weekly alcohol intake during pregnancy, but only for interviews carried out during working hours (table 7). None of the other results given in tables 4 and 5 changed after this stratification (data not shown).
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TABLE 6. Characteristics of interviewers according to the timing of the interview, Danish National Birth Cohort Study, 19971999
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TABLE 7. Respondents' reported alcohol drinking during pregnancy (%) according to interviewers' alcohol-drinking habits, stratified by the timing of the interview, Danish National Birth Cohort Study, 19971999
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DISCUSSION
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We did not find any significant associations between interviewers' smoking habits, alcohol consumption, attitudes toward smoking and drinking during pregnancy, or demographic characteristics and the answers they obtained from pregnant women about smoking and alcohol consumption. Only one subanalysis showed a statistically significant association, which may have been due to chance. The association showed no trend, and it disappeared if the answer categories were modified slightly.
Responses to questions on smoking and alcohol drinking in pregnancy were chosen because they were thought to be most likely to produce an interviewer effect. Alcohol drinking and tobacco smoking during pregnancy are undesirable habits, and respondents might be inclined to minimize these habits and give more socially desirable responses (3
).
Studies on interviewer variation according to demographic variables have shown conflicting results (7
). Johnson et al. (8
) found an association between reporting of substance use and the interviewer's age and race: Caucasians and older interviewers obtained more reports of substance use. Johannes et al. (9
) found minor but significant interviewer variation in the Massachusetts Women's Health Study. The interviewers were similar regarding age and education but differed in terms of interviewing experience. Freeman and Butler (10
) intended to include interviewer's sex, age, socioeconomic status, and ideology in a study of interviewer effects. They found interviewer variation according to sex and age, but the beliefs and experiences of the interviewers were too homogenous to be analyzed (10
). We are not aware of any other studies that have addressed potential biases arising from interviewers' own habits and personal beliefs.
If an interviewer effect is present, it should be adjusted for, but this is only possible if its determinants are known and recorded. Johannes et al. (9
) recommended examining data for interviewer effects and showed how adjustment for interviewer effects changed one of the conclusions of a specific study.
The absence of an interviewer effect in this study may be due to the design of the Danish National Birth Cohort Study. We used exclusively female interviewers to avoid gender-based interviewer effects (8
), and the interviewers were all of reproductive age (11
). The interviews were carried out in a centralized setting with continuous supervision, and the educational program for the interviewers included a lecture on how to avoid interviewer effects. The interviewers were given standardized ways of reformulating a question if it was not initially understood, as well as rules about how to interpret ambiguous answers. Use of a highly structured questionnaire with closed answering categories may also have contributed to these results.
In this study, interviewer effects arising from variations in interviewers' demographic characteristics, health beliefs, and personal habits were found to be negligible in computer-assisted telephone interviews from a large epidemiologic project. Several precautions were taken to avoid interviewer-associated bias, and these measures may have contributed to the results.
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ACKNOWLEDGMENTS
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The activities of the Danish Epidemiology Science Centre are financed by a grant from the Danish National Research Foundation.
The authors thank Drs. Per Kragh Andersen and Sjurdur F. Olsen of the Danish Epidemiology Science Centre for valuable comments on the study methodology. The authors also thank the study interviewers for their contributions.
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NOTES
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Reprint requests to Dr. Anne-Marie Nybo Andersen, Department of Social Medicine, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark (e-mail: a.nybo{at}pubhealth.ku.dk).
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REFERENCES
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-
Bradburn NM, Sudman S. Interviewer variation in asking questions. In: Bradburn NM, Sudman S, eds. Improving interview method and questionnaire design. San Francisco, CA: Jossey-Bass Publishers, 1979:2650.
-
Cartwright A. Interviews or postal questionnaires? Comparisons of data about women's experiences with maternity services. Milbank Q 1988;66:17289.[ISI][Medline]
-
Lyberg LE, Kasprzyk D. Data collection methods and measurement error: an overview. In: Biemer PB, Sudman S, Groves RM, et al, eds. Measurement errors in surveys. New York, NY: John Wiley and Sons, Inc, 1991:23757.
-
Frey JH. Survey research by telephone. 2nd ed. Newbury Park, CA: Sage Publications, 1989.
-
Körmendi E, Noordhoek J. Data quality and telephone interviews. Copenhagen, Denmark: Danmarks Statistik, 1989.
-
Olsen J. Epidemiology deserves better questionnaires. IEA European Questionnaire Group. Int J Epidemiol 1998;27:935.[Free Full Text]
-
Singer E, Frankel MR, Glassman MB. The effect of interviewer characteristics and expectations on response. Public Opin Q 1983;47:6883.[Abstract]
-
Johnson TP, Parsons JA. Interviewer effects on self-reported substance use among homeless persons. Addict Behav 1994;19:8393.[ISI][Medline]
-
Johannes CB, Crawford SL, McKinlay JB. Interviewer effects in a cohort study: results from the Massachusetts Women's Health Study. Am J Epidemiol 1997;146:42938.[Abstract]
-
Freeman J, Butler EW. Some sources of interviewer variance in surveys. Public Opin Q 1976;40:7991.[Abstract]
-
Kane EW, Macaulay LJ. Interviewer gender and gender attitudes. Public Opin Q 1993;57:128.[Abstract]
Received for publication August 8, 2000.
Accepted for publication June 26, 2001.