Public Health Information Network PHIN Series II

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Public Health Information Network (PHIN) Series
II

• Outbreak Investigation Methods
• From Mystery to Mastery

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(No Transcript)
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Access Series Files Online http//www.vdh.virgini
a.gov/EPR/Training.asp

• Session slides
• Session activities (when applicable)
• Session evaluation forms
• Speaker biographies
• Alternate Web site http//www.sph.unc.edu/nccphp/
  phtin/index.htm

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Site Sign-in Sheet

• Please submit your site sign-in sheet and
• session evaluation forms to
• Suzi Silverstein
• Director, Education and Training
• Emergency Preparedness Response Programs
• FAX (804) 225 - 3888

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Series IISession V

• Interviewing Techniques

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Series II Sessions
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CDCOutbreak Management System
Software Support National Center for Public
Health Informatics outbreakms_at_cdc.gov / (800)
532-9929, option 6
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OMS Applications

• Track demographics, case investigations, and
  exposure contact relationships for persons,
  animals, events, travel events, vehicles,
  objects, organizations, other organisms, and
  locations.
• Create household, social, or occupational
  relationships among records
• Run OMS on desktops or laptops CAPI

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OMS User Interface
Source http//www.cdc.gov/phin/software-solutio
ns/oms/index.html
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OMS User Interface
Source http//www.cdc.gov/phin/software-solution
s/oms/index.html
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OMS in Virginia

• Contact
• Michael A. Coletta, MPH
• Bioterrorism Surveillance Coordinator
• Division of Surveillance and Investigation
• Office of Epidemiology
• Telephone [phone]
• Email michael.coletta_at_vdh.virginia.gov

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Todays Presenters

• Aaron Wendelboe, MSPH
• Doctoral Candidate and
• Graduate Research Assistant,
• NC Center for Public Health Preparedness
• Erin Rothney, MPH
• Research Associate,
• NC Center for Public Health Preparedness

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Interviewing Techniques Learning Objectives

• Upon completion of this session, you will
• Recognize the interrelatedness of interview
  techniques and questionnaire design
• Understand key survey research terms
• Understand the advantages and disadvantages of
  face-to-face, telephone, and computer assisted
  interview methods

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Learning Objectives (contd.)

• Understand the advantages and disadvantages of
  mail and Web-based survey implementation
• Know what to address in interviewer training
• Recognize good interview techniques
• Understand confidentiality concerns from the
  perspectives of both the respondent and the
  outbreak investigator

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Lecturer

• Aaron Wendelboe, MSPH
• Doctoral Candidate and
• Graduate Research Assistant,
• NC Center for Public Health Preparedness

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Basic Steps of an Outbreak Investigation

• Verify the diagnosis and confirm the outbreak
• Define a case and conduct case finding
• Tabulate and orient data time, place, person
• Take immediate control measures
• Formulate and test hypothesis
• Plan and execute additional studies
• Implement and evaluate control measures
• Communicate findings

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Interviewing Techniques

• Introduction

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Introduction

• The role of interviews in outbreak investigations
• Types of interviewing methods
• Interrelatedness of interview method and
  questionnaire design
• Key survey research concepts
• Sampling
• Response rates

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Role of Interviews in Outbreak Investigations

• Primary purpose data collection
• Case identification
• Risk factor identification
• Hypothesis generation

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Interviewing Methods

• Interviewer Administered
• Face-to-face
• Telephone
• Self Administered
• Mail-out
• Email
• Web-based
• Combination of 1 and 2

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Questionnaire Design

• Interview Method Influenced by
• Length and format of questionnaire
• Question types used in a survey
• Cost considerations for survey implementation

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Sampling
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Sampling

• Sampling is the systematic selection of a
  portion of the larger source population. A
  sample should be representative of the larger
  source population.

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Sampling
Source Pop Students (12,000)
Sampled pop (150 students)
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Sampling

• Why Sample?
• Because it is more efficient saves time and
  money!

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Sampling

• Sample size
• Is the purpose of the study to determine the
  source of the outbreak?
• A small number of cases and controls can reveal
  risk factors for infection.
• Is the purpose of the study to determine the
  number of persons who become sick over a specific
  period of time attack rate?
• A cohort study would require a larger sample.

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Sampling

• Types of Sampling
• Simple Random Sample (SRS)
• Randomly select persons to participate in study.
  There are many variations of SRS.
• Convenience Sample
• Choose those individuals who are easily
  accessible.

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Sampling

• Problems with Convenience Sampling
• Based on subjective judgment
• Cases may or may not be representative of the
  total population
• May lead to biased results

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Sampling

• Additional Resources
• http//www.sph.unc.edu/nccphp/training/all_trainin
  gs/at_sampl.htm
• Sampling Case Studies
• Survey Sampling Precision, Sample Size, and
  Conducting a Survey
• Survey Sampling Terminology and Methods

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Response Rates
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Response Rates

• Response rates measure the percentage of your
  sample that has participated in your survey.
• Example
• Using the campus directory, you email a survey
  to a random sample of 100 freshmen. 40 of those
  students complete the survey and return it
  electronically. Your response rate is 40.

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Response Rates

• High response rates ensure that survey data are
  representative of the source population, and that
  results will be valid.

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Response Rates

• Types of Non-response
• Non-contact No one at home
• Refusal to participate
• Inability to participate (due to language barrier
  or physical or mental condition)

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Response Rates

• What is an average response rate?

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Response Rates

• Determining Response Rates
• Refer to the American Association of Public
  Opinion Research website www.aapor.org
• Link to the document titled, Standard
  definitions from the home page.

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Interviewer AdministeredData Collection
Considerations
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Interviewer Administered Data Collection

• Advantages and disadvantages of
• face-to-face interviews
• Advantages and disadvantages of telephone
  interviews
• Advantages and disadvantages of Computer assisted
  interviews

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Face-to-Face Interview

• Advantages
• Higher response rate
• Longer survey instrument
• Can have more complex skip patterns
• More accurate recording of responses
• Less item non-response
• Appropriate for hard to reach populations (e.g.,
  illiterate, institutionalized)

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Face-to-Face Interview

• Disadvantages
• Costly
• Potential for interviewer error
• Less anonymous than self-administered
• Potential for dishonesty

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Telephone Interview

• Advantages
• Less costly than face-to-face
• Higher response rates than mailed
• Quicker access to participants
• Supervision of interviewers feasible
• Can collect more sensitive information
• Survey design can be more efficient

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Telephone Interview

• Disadvantages
• Lower response rates than face-to-face
• Shorter questionnaires used
• Unable to capture important visual information
  (e.g., rash, working conditions)
• Under-coverage (e.g., population without phones)
• 2.1 of total population in Virginia

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Computer Assisted Interviewing (CAI)

• CATI Telephone
• CAPI Personal
• ACASI Audio

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CAPI ExampleNC PHRST Teams

• NC PHRST Team public health professionals use
  PDAs for rapid needs assessment face-to-face
  interviews.
• PDA Personal Digital Assistant, also sometimes
  called hand-held computers, palmtops, and pocket
  computers

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Field Data Collection
EPI Info GIS
Wireless WIFI 802.11 or Bluetooth
Field Team 4
Field Team 5
Field Team 1
Field Team 2
Field Team 3
Field data collection using IPAQ Pocket PCs
equipped with GPS, GIS software and data
collection forms.
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vs.

• Pros
• Inexpensive
• No special skills required for data recording
• Cons
• Requires double data-entry
• Greater risk of data errors
• Clipboard and paper more cumbersome in the field

• Pros
• Eliminates double data entry
• Provides routing and direction-finding for field
  teams
• Improved randomization through GIS
• Ability to quickly analyze and map data
• Cons
• Technology is expensive
• Learning curve / required training for data entry
• Small screen size requires scrolling through many
  questionnaire pages

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For More Information. . .

• Steven Ramsey, RS
• Team Leader / Industrial Hygienist
• PHRST-5
• Guilford County Health Department, NC
• (336) -641-8192

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Self AdministeredData Collection Considerations
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Self-administeredData Collection

• Advantages and disadvantages of
• mailed questionnaires
• Advantages and disadvantages of
• Web-based questionnaires

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Mailed Questionnaire

• Advantages
• More anonymous
• May collect more honest responses
• No interviewer error
• Less expensive
• Respondent has more time to think about question

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Mailed Questionnaire

• Disadvantages
• Questionnaire must be simple
• Higher item non-response
• Lower response rate
• Data collection takes more time
• Sample population must be literate
• Coverage / frame deficiencies

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Web-based Questionnaire

• Advantages
• Among some populations, most people may have
  access to the Web / email
• Inexpensive and fast
• No data entry required
• Improves data quality
• Many vendors send data in a variety of formats

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Web-based Questionnaire

• Disadvantages
• Mandatory access to and experience with Internet
• Potential connection speed and hardware /
  software capacity limitations
• Potential for multiple responses from one
  individual
• Potential for responses from non-sampled
  respondents
• Need email address list to contact sample

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Web-based Questionnaire

• Example Dartmouth University 698 (13.8) of
  5060 students had conjunctivitis in spring 2002
• To identify risk factors...
• web-based questionnaire set up
• E-mail sent to 3682 undergraduates
• No data entry - rapid analysis
• 1832 responded (50 response rate)
• -- Source An outbreak of conjunctivitis due
  to atypical Streptococcus
• pneumoniae. N Engl J Med. 2003348 (12)1112-21.
  

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Web-based Questionnaire

• For a list of vendors that provide Web-based
  survey tools, please visit
• http//www.surveymonkey.com/Pricing.asp

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Question and Answer Opportunity
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5 minute break
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Standardizing Interviews
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Standardizing Interviews

• The goal of standardization is to help minimize
  error, thereby yielding better data quality
• Minimizing interviewer error is done through
  making surveys more standard or consistent

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Error

• Interviewer Error
• Deviation from expected answer due to the
  effects of interviewers.

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Interviewer ErrorExample Gonorrhea outbreak

• Bias
• Interviewers probe on the sexual history
  section more among non-whites than whites

• Variance
• A male interviewer may elicit different
  responses from a female respondent than a female
  interviewer.

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Error

• Additional Resource
• Schwarz, N., Groves, R., and Schuman, H.,
  Survey Methods Chapter 4 in Gilbert, D. et al
  (Eds) (1998). The Handbook of Social Psychology.
  Boston McGraw-Hill pp 143 179.

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Standardizing Interviews

• Contributing Factors
• Question wording
• Interviewer selection
• Interviewer training
• Interviewing procedures
• Supervising interviewers

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1. Question Wording
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Question Wording

• Criteria for Standardized Interview Questions
• Must be fully scripted
• Must mean the same thing to every respondent

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2. Interviewer Selection
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Interviewer Selection

• Criteria for Telephone Interviewer Selection
• Ability to read questions fluently
• Clear and pleasant telephone voice
• Responds quickly to respondents questions
• Reliability

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Criteria for Face-to-FaceInterviewer Selection

• Logistical skills (reading maps)
• Good interpersonal skills
• Independent workers
• Reliability
• In certain circumstances, parallel demographic
  characteristics among interviewers and
  interviewees

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3. Interviewer Training
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Interviewer Training

• Training is NOT optional!
• Trainings must be interactive
• Interviewers must practice reading questions out
  loud
• Provide support documentation (manual)

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Interviewer TrainingElements

• Purpose of survey
• How to use data collection instrument
• Respondent selection process
• Intent and meaning of each question
• How to record/code responses
• Administering questionnaire
• Addressing participants questions
• Methods for improving response rate
• Tracking calls / completed surveys / call- backs
• Confidentiality

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Interviewer Training

• Respondent Selection Process
• Provide proxy respondent rules for adults and
  children because proxy response impacts
• Data quality
• Sampling

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Interviewer Training

• Questionnaire Administration
• To establish legitimacy of the survey upon first
  contact, tell the respondent
• Who is calling
• What is requested
• Why respondent should cooperate
• How respondent was chosen

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Interviewer TrainingLogistics

• Face-to-Face
• Reading maps
• Getting to respondents homes
• Reimbursement
• Dress code
• Scheduling callbacks

• Telephone
• Operation of equipment
• Operation of CATI software (if applicable)

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Interviewer Training

• Other Considerations
• Record some resolution to each question
• Are missing responses due to skip patterns or
  errors?
• Review interview after completion
• Missing responses
• Illegible responses

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Interviewer Training

• Interviewer Manual
• An interviewer manual serves as a reference to
  interviewers during interviews and as survey
  documentation.

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Interviewer Training

• Suggested Interviewer Manual Contents
• Background information
• Fieldwork
• Interviewing techniques
• Survey instrument terms and definitions

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Interviewer Training Program Example

• Behavioral Risk Factor Surveillance System (BRFSS)

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BRFSS Interviewer Training

• On-line training covers
• Why BRFSS data are important, how data are used
• Interviewer responsibilities
• Nuts and bolts of the interviewing process
• Interviewing techniques

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BRFSS Interviewer Training

• On-line interviewer training available at
• http//apps.nccd.cdc.gov/BRFSS_Training_Int/overv
  iew.asp
• General information about BRFSS
  http//www.cdc.gov/brfss/

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4. Interviewing Procedures
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Interviewing Procedures

• Rules
• Read questions exactly as worded
• Probe inadequate answers, if necessary
• Record answers without interviewer discretion
• Maintain rapport with respondents
• Maintain an even pace

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Interviewing Procedures

• Read questions exactly
• Read entire question before accepting an answer
• Clarify questions if necessary

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Interviewing Procedures

• Read questions exactly
• Use only standard definitions / clarification
  provided
• Use the phrase Whatever x means to you, OR
  Whatever you think of as x.
• When asked to repeat only one of several response
  options, repeat ALL options given for a question

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Interviewing Procedures

• Probe
• A probe is a standardized way to obtain
  additional information from a respondent.
• Use probes when a respondents answer is unclear
  or irrelevant.

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Probe

• Examples of responses requiring a probe
  Interviewer "In the past two weeks, have you
  been swimming in a public pool?
• Irrelevant Response I swam in a lake at a
  national park last month."
• Unclear Response I stayed in a hotel with a
  pool when I was on vacation last week."

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Interviewing Procedures

• Standard Probe Examples
• Repeat the question
• Retrieve receipts / calendars
• What do you mean? How do you mean?
• If respondent has narrowed down answer
• Which would be closer?
• If you had to choose, which would you pick?

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Interviewing Procedures

• Recording Answers
• Do not direct respondent toward an answer
  (leading)
• Do not assume that an answer received in
  passing is correct
• Do not skip questions, even if answer was given
  earlier
• Do not remind respondent of earlier remark if
  answer differs from what you expect

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Probing versus Leading

• Example
• Interviewer In the last 7 days, how many times
  did you eat prepared food at the dorm cafeteria?
  Would you say
• None d. 3 times
• Once e. More than 3 times
• Twice
• Respondent
• Oh, gee, I didnt go very often . . . maybe a
  few times.

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Probing versus Leading

• Example
• Interviewer Probe (correct)
• Which would be closer none, once, twice, 3
  times, or more than 3 times?
• Interviewer Leading (incorrect)
• So, would you say twice, or three times?
• b. Do you mean twice, or three times?

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Interviewing Procedures

• Maintain Rapport
• An interviewer should be
• Nonjudgmental
• Noncommittal
• Objective

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Maintain Rapport

• Any line can be said a thousand ways.
• - BRFSS interviewer training
• Interviewers can put respondents at ease by
  doing the following
• Read the questions in a friendly, natural manner
• Speak at a moderate rate of speed
• Sound interested
• Strive for a low-pitched voice

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Feedback Helps Maintain Rapport

• Feedback is a statement or action that indicates
  to the respondent that s/he is doing a good job.
• Give feedback only for acceptable performance -
  not good" content.
• Give short feedback phrases for short responses,
  longer feedback for longer responses.
• Specific study information and interviewer
  task-related comments can serve as feedback.
• Telephone interviewers should give feedback for
  acceptable respondent performance 30-50 of the
  time.

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Feedback Examples

• I see
• Uh-huh
• Thank you / Thanks
• That is useful / helpful information
• I see, that is helpful to know
• That is useful for our research
• Let me get that down
• I want to make sure I have that right (REPEAT
  ANSWER)
• We have touched on this before, but I need to
  ask every question in the order that it appears
  in the questionnaire

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Interviewing Procedures

• Maintain Even Pace
• Pace refers to the rate of progression of the
  interview.
• Pace can vary by question type.
• Let the respondent set the pace.

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Question and Answer Opportunity
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Activity Correct Interview ProceduresProbing
vs. Leading vs. Feedback

• Completion time 5 minutes

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Activity

• Interviewer Are you still experiencing
  Diarrhea?
• Respondent 1 Im not sure
• Respondent 2 I definitely had diarrhea last
  Tuesday
• Respondent 3 Yes
• Activity Instructions
• How should the interviewer respond to these 3
  answers? Provide an example of either a
  clarification, probe, or feedback that the
  interviewer could use. Try to think of one
  correct use of each technique.

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Activity

• Suggested Answer
• Respondent 1 Im not sure
• Try a clarification
• For the purposes of this survey, we consider
  diarrhea to be 3 or more loose bowel movements in
  a 24 hour period.

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Activity

• Suggested Answer
• Respondent 2
• I definitely had diarrhea last Tuesday
• Try a Probe
• OK, but are you still experiencing diarrhea?

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Activity

• Suggested Answer
• Respondent 3 Yes
• Good Feedback I see
• Bad Feedback Are you sure? (leading)

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5. Supervising Interviewers
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Supervising Interviewers

• Monitoring, evaluation, and feedback given to
  interviewers should focus on the way interviewers
  handle the question-answer process.

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Other Supervision Tasks

• Scheduling interviewers
• Number of interviewers needed
• Time calls / visits will be made
• Setting up interview space
• Tracking who has been called and who has not
• Reviewing data from completed interviews

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Confidentiality
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Confidentiality

• Human Subjects Informed Consent
• Outbreak investigations are considered a public
  health emergency, with the purpose of identifying
  and controlling a health problem. Informed
  consent or Institutional Review Board (IRB)
  clearance are not required.

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Confidentiality

• Human Subjects Informed Consent
• If further analysis of outbreak investigation
  data is conducted for the purpose of research,
  IRB approval should be obtained.

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Confidentiality

• Respondent Perspective
• Opening statement of every interview should
  indicate that all information collected will be
  kept confidential.

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Confidentiality

• Outbreak Investigation Perspective
• Do not discuss details about the outbreak
• Provide only a brief description of the purpose
  of the survey at first contact

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Question and Answer Opportunity
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5 minute break
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Guest Lecturer

• Erin Rothney, MPH
• Research Associate
• NC Center for Public Health Preparedness

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Overview

• Provide real-life examples of situations where
  you will use interviewing techniques
• Face-to-face interviewing
• Telephone interviewing
• Discuss advantages and disadvantages
• Compare interviewing methods

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Face-to-face Interviews
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Community Assessments

• Identify the needs and strengths of a particular
  community from several stakeholder perspectives
• Include interviewing community members and
  observing the environmental and individual
  characteristics and community infrastructure
• Similar to rapid needs assessments, but completed
  within a longer time frame

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Durham, NCCommunity Assessment

• Fall 2002 - Spring 2003
• Bragtown Neighborhood, Durham, NC
• 5 person team
• Interviewed residents and other stakeholders in
  Bragtown
• 4 page survey, 60 minutes in length

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Durham, NCCommunity Assessment

• Tasks
• Questionnaire design
• Interviewer training
• Interviewing
• Facilitating focus groups
• Analyzing data
• Presenting data to the community

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Survey Instrument

• Question Examples
• Life in the Community
• What do people in Bragtown do for recreation?
• What types of religion are practiced in Bragtown?
• What do people in Bragtown do for a living?
• What political or government organizations exist
  in Bragtown?
• What different cultural and ethnic groups live in
  Bragtown?
• How do these different groups interact? Do they
  get along?
• Community Assets
• What do you like about Bragtown?
• What are some organizations within your community
  that positively affect you or your community?
• Probe What about political groups,
  environmental groups, church groups?
• Who are the individuals within your community
  that you feel are positive leaders or role
  models?
• Probe Any others?

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Interviewer Training

• Active listening skills
• Showing empathy
• Using probes
• Practice interviewing, not just reading questions

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Face-to-face Interviews

• Challenges
• Hard to find people at home
• People may not want to invite a stranger into
  their home
• Costly and time-intensive method of interviewing

• Solutions
• Schedule time ahead by phone or stop by and
  schedule more convenient time
• Use the skills you learned in interviewer
  training to gain trust
• Have someone on staff train others on
  interviewing techniques carpool set time limits

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Lessons Learned

• Study community demographics and characteristics
  before you interview
• Train interviewers before an immediate need
• People like to tell you their stories- could lead
  to relevant information

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Telephone Interviews2004 E. coli Outbreak
Investigation
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E. coli Outbreak Investigation Telephone
Interviews

• Illness onset October - November 2004
• Geographically dispersed cases in multiple states
• Case-control study
• Train-the-trainer, interviewer

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E. coli Outbreak InvestigationTelephone
Interviews

• Between 3 and 6 interviewers
• Calls made between 3 p.m. and 8 p.m.
• Quality control with one central interviewing
  location
• News coverage piqued peoples interest in the
  outbreak investigation

126
Lessons Learned

• Practice reading through the questions and
  conducting an interview
• The media can be your friend
• Use an introductory script to relate the purpose
  of the phone call to the individual quickly
• Identify and legitimize the interviewer
• State reasons for conducting the survey
• Assure that responses will be confidential

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Summary

• Telephone
• Outbreak Investigation
• News coverage helped in recruiting people to
  participate
• Widely distributed sample
• We had the phone numbers of all the people who
  pre-bought tickets

• Face-to-face
• Community Assessment
• Establish rapport
• Identify people in a small geographic area
• Assess the environment of the area

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Question and Answer Opportunity
129
Session Summary
130
Session Summary

• Questionnaire design and interview methods are
  interrelated in the overall process of an
  outbreak investigation.
• The primary purpose of interviews in outbreak
  investigations is to collect data for case
  identification, risk factor identification, or
  hypothesis generation.

131
Session Summary

• Interview methods can be interviewer administered
  (face-to-face or telephone) or self administered
  (mailed, emailed, or Web-based). There are
  advantages and disadvantages to employing either
  method.
• Sampling is the systematic selection of a
  representative portion of the larger source
  population to be interviewed. If the purpose of
  your study is to determine the point source of
  infection, you may be able to interview a smaller
  sample if the purpose of your study is to
  calculate an attack rate, you may need to
  interview a larger sample.

132
Session Summary

• Survey response rates measure the percentage of
  your sample that has participated in your survey.
  Average response rates vary from as little as
  56 for mailed surveys to 75 for face-to-face
  surveys.
• Non-response to surveys can be a result of no one
  being home, refusal to participate, or individual
  inability to participate (e.g., because of a
  language barrier or physical or mental
  condition).

133
Session Summary

• Survey data collection error is a result of both
  bias and variance in the interview process.
• Interviewer error can be prevented with adequate
  interviewer training and the standardization of
  survey instruments.

134
Session Summary

• Develop and distribute an interviewer manual to
  provide interviewer support. Such documentation
  reduces error and enhances the quality of data
  collected.
• Sound interviewing procedures include reading
  questions exactly as they are worded probing
  inadequate answers recording answers without
  interviewer discretion and maintaining rapport
  with respondents.

135
Next Session November 3rd100 p.m. 300 p.m.

• Topic Analyzing Data

136
References and Resources

• American Statistical Association (1997). What Is
  a Survey? More About Mail Surveys. Alexandria,
  VA Section on Survey Research Methods, American
  Statistical Association.
• American Statistical Association (1997). What Is
  a Survey? How to Collect Survey Data.
  Alexandria, VA Section on Survey Research
  Methods, American Statistical Association.
• Centers for Disease Control and Prevention
  (2005). Outbreak Management System Demonstration
  Web site. http//www.cdc.gov/phin/software-soluti
  ons/oms/index.html.

137
References and Resources

• Fowler, F. and Mangione, T. (1990).
  Standardizing Survey Interviewing. Newbury Park
  Sage Publications.
• Gregg, M. (ed). (1996). Field Epidemiology.
  Oxford University Press.
• Holstein, JA and Gubrium, JF. (1997). Active
  Interviewing. In Silverman, D. (Ed.) Qualitative
  Research Theory, Method, and Practice. London
  Sage Publications, pp. 113-129.
• Last, J.M. (2001). A Dictionary of Epidemiology
  4th Edition. Oxford University Press New York.

138
References and Resources

• Levy, P. and Lemeshow, S. (1991). Sampling of
  Populations. John Wiley Sons.
• Ramsey, S. et al (2005). Using GIS and GPS to
  Improve Public Health Response. Guilford County,
  NC Health Department Public Health Regional
  Surveillance Team 5.
• Rubin, HJ and Rubin, IS.  (1995). Interviews as
  Guided Conversations. Qualitative Interviewing
  The Art of Hearing Data. Sage Publications, pp.
  1-16, 122-144.
• Salant, P. and Dillman, D. (1994). How to
  Conduct Your Own Survey. John Wiley Sons.

139
References and Resources

• Stehr-Green, J.K. (2002). Gastroenteritis at a
  University in Texas Case Study Instructors
  Guide. Atlanta, GA U.S. Department of Health
  and Human Services, Public Health Service,
  Centers for Disease Control and Prevention.
• U.S. Census Bureau (2005). Profile of Selected
  Housing Characteristics by State Census 2000
  Summary File 3 http//factfinder.census.gov/servle
  t/QTTable?_bmn_langenqr_nameDEC_2000_SF3_U_DP
  4ds_nameDEC_2000_SF3_Ugeo_id04000US51
• Weiss, R.S. (1994). Learning from Strangers The
  Art and Method of Qualitative Interview Studies.
  New York The Free Press.
• Wiggins, B. and Deeb-Sossa, N. (2000).
  Conducting Telephone Surveys. Chapel Hill, NC
  Odum Institute for Research in Social Science.