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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Series IISession IV

• Designing Questionnaires

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Series II Sessions
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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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Session Overview

• The importance of questionnaire design
• Hypothesis generating versus hypothesis testing
  questionnaires
• Preparing for questionnaire design
• Question design
• Question type
• Questionnaire format

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Todays Presenters

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

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Learning Objectives

• Upon completion of this session, you will
• Understand the role of questionnaire design in an
  outbreak investigation
• Know how to develop a hypothesis generating
  questionnaire
• Recognize key planning strategies for successful
  questionnaire design

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Learning Objectives

• Recognize key characteristics of well-designed
  questions
• Recognize three broad question types and when to
  use them
• Understand what different question types measure,
  and the type of data (quantitative versus
  qualitative) they yield

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Learning Objectives

• Know how to format questionnaires for interviewer
  administered and self-administered settings

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Session IV

• Designing Questionnaires

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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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Why is Questionnaire Design Important?

• The quality of the data will be no better than
  the most error-prone feature of the survey
  design.
• - Fowler, F.J. (1993). Survey Research Methods
  Second Edition. Sage Publications Newbury
  Park.

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Why is Questionnaire Design Important?

• With an understanding of good questionnaire
  design principles, you will ask only about what
  you need to meet your research objectives.

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Ask Only About What You Need. . .

• Example
• You ask respondents to list all vaccinations
  that their school-aged child has had (difficult
  in terms of respondent recall / accuracy), when
  you really only need to know if the child is
  current on all DTP boosters.

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Why is Questionnaire Design Important?

• Survey answers are not of interest
  intrinsically rather, the answers are important
  because of their relationship to what they are
  supposed to help you measure.

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Why is Questionnaire Design Important?

• Question type and response option formatting
  impact
• 1. How you can design an on-screen data entry
  form and / or analyze variables in your software
  program
• 2. How respondents interpret and respond to the
  questions

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Hypothesis Generating Questionnaires
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Which Questionnaire Type Should You Use?

• Hypothesis Generating?
• Hypothesis Testing?

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Hypothesis Generating Questionnaire

• Person, Place, Time Questions
• Demographics
• Clinical details of the illness
• Health care provider visits
• Water exposure
• Exposure to other ill persons
• Exposure to children in day care
• Exposure to a farm or farm animals
• Travel outside of the immediate area

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Hypothesis Generating Questionnaire

• If the pathogen can be spread through food or
  beverages, include questions about
• Food eaten in the home
• Food eaten in the homes of friends, family
• Food eaten at any restaurant
• Dates and times of food consumption and any
  suspicious observations

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Hypothesis Generating Questionnaire
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Hypothesis Generating Questionnaire
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Hypothesis Testing Questionnaires
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Hypothesis Testing Questionnaire

• Include detailed questions about the suspected
  source of infection.
• Example The local bakery is suspected as the
  source of a Hepatitis outbreak in multiple
  counties. The hypothesis testing questionnaire
  is used with both cases and non-cases, and
  includes only a food history for all possible
  items on the bakery menu to pinpoint the exact
  food item that is contaminated.

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Hypothesis Testing Questionnaire
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Hypothesis Generating versus Testing Questions
E. coli 0157H7

• Hypothesis Generating
• Account for consumption of ground beef, lettuce,
  alfalfa sprouts, un-pasteurized milk or juice,
  and swimming in or drinking sewage-contaminated
  water

• Hypothesis Testing
• beef suspected
• Beef brand, date of purchase, and grocery store
  or restaurant where beef was purchased or eaten

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Preparing for Questionnaire Design
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Preparing for Questionnaire Design

• There is more to questionnaire design than
  writing questions. Ideally, you should first
• Have a clear purpose and research objectives
• List variables to be measured
• Have an analysis plan
• Consider cost and other logistical aspects

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Questionnaire Design

• Have a clear purpose and research objectives.
• Is the purpose of your outbreak investigation
  survey to generate a hypothesis or to test a
  refined hypothesis?
• If testing a hypothesis, who is included in your
  study sample?

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Questionnaire Design

• List variables to be measured
• Whether you are generating or testing a
  hypothesis, determine your variables of interest
  before you develop questions. You will avoid
  asking unnecessary questions or asking for
  unnecessary details.

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Questionnaire Design

• Go to http//www.cdc.gov
• Under Health Safety Topics in the left
  margin, click on, Diseases Conditions
• Select a link to either an alphabetized list of
  all diseases or diseases by topic e.g., if you
  already know that a pathogen is water-borne
  versus food-borne

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Questionnaire Design
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Questionnaire Design

• Have an analysis plan.
• Guides the question types and response option
  categories used on the questionnaire
• Helps assure that the data collection leading up
  to analysis yields variable coding that your
  analysis software program can use efficiently.

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Questionnaire Design

• Analysis Plan
• Hypothesis
• Variables involved
• Response option coding
• Continuous versus categorical values

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Questionnaire Design

• Consider cost and other logistical aspects
• What is the survey sample size?
• What is the geographic distribution of the survey
  sample?
• Will questionnaires be interviewer administered
  or self-administered?
• What is your staff capacity to work within the
  parameters of a c above?

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Question Answer Opportunity
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Question Design
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Elements of Good Question Design

• Reliability
• Validity
• Specificity versus ambiguity
• Simplicity
• Only one question asked
• Mutually exclusive answer choices
• Refers respondents to specific dates / times for
  recall
• When feasible, make sure data can be compared to
  existing sources of information

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Question Design

• 1. A question that is designed to be reliable
  will assure that the words are interpreted the
  same way in any setting, and that respondents
  answer the same way in any setting.

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Reliable Question Design

• Question
• Are you experiencing diarrhea?
• Interviewer then adds
• 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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Question Design

• 2. A question that is designed to be valid will
  always yield information that can be used as a
  true measure of what you, the researcher, are
  looking for.

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Valid Question Design

• Less Useful
• Which is your source of drinking water at home?
• Tap water
• Bottled water
• Better
• Which is your source of drinking water at home?
• Municipal tap water
• Municipal tap water with additional filtration
• Well water
• Commercially bottled water

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Question Design

• 3. Avoid ambiguity in question wording.
• Less useful
• When did you have Disease X?
• Better
• How old were you when you had Disease X?

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Question Design

• 3. Avoid ambiguity in question wording.
• Less useful
• Have you been examined by a physician in the
  past seven days?
• Better
• Have you been examined by a physician for these
  symptoms in the past seven days?

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Question Design

• 4. Use simple language and keep questions
  short.
• Less useful
• Were you exposed to the fomite at the dinner
  party?
• Better
• Did you use a shared hand towel at the dinner
  party?

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Question Design

• 5. Ask only one question.
• Two questions in one
• Did you eat mashed potatoes and giblet gravy?
• One question at a time
• Did you eat mashed potatoes? Yes No
• If Yes, did you eat them
• a. Plain
• b. With giblet gravy

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Question Design

• 6. For closed-ended questions, make sure that
  response options are mutually exclusive.
• Not useful
• What is your age?
• 18 years
• Useful
• What is your age?
• 17 years old or younger
• 18 years old or older

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Question Design

• 7. Use specific date / time references to
  improve respondent recall.
• Less useful
• Have you been swimming in a public pool
  recently?
• Better
• Did you swim in a public pool any time between
  Friday, July 1st and Monday, July 4th?

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Question Design

• When feasible, make sure data can be compared to
  existing sources of information.
• Example
• Case-patient age
• Less than 2 years
• 2 5 years
• The U.S. Census reports population data for age
  groups
• less than 1
• 1 2
• 3
• 4
• 5

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Question DesignGeneral Guidelines

• Design clear (unambiguous), specific questions.
• Use simple language and keep questions short.
• Ask only one question!

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Question DesignGeneral Guidelines

• For closed-ended questions, make sure that
  response options are mutually exclusive.
• Use specific date / time references to improve
  respondent recall.
• Make sure data can be compared to existing
  sources of information if you need to compare
  local, state, and national statistics.

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Question Type
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Question Type

• Three broad categories
• Closed-ended
• Open-ended
• Fill-in-the-blank
• Data collected and analysis options may differ
  by question type.

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Closed-ended Questions
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Closed-Ended Questions

• Provide answer choices in pre-coded categories
  that represent counts, ranges, or demographic
  information.
• Yield quantitative data.
• Are preferable for self-administered and
  hypothesis testing questionnaires.

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Closed-Ended Questions

• Example Pre-coded demographic information
• In which of the following categories does your
  age fall? (select only one)
• 0 20
• 21 40
• 41 60
• 61 - 80
• 81 100

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Question Type

• There are two ways in which categorical
  measurement is carried out in closed-ended
  questions
• Nominal
• Ordinal

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Question Type

• Nominal response options result in the
  classification of a respondent into a category
  for race, gender, marital status, etc.
• - Response options can be mutually exclusive
  (Select only one response)

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Question Type

• Example Nominal response options in a
  closed-ended question
• Please select the one response that describes
  your marital status.
• Single
• Married
• Divorced
• Widowed

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Question Type

• Ordinal response options result in
  classification into an ordered category that may
  or may not rank values that are equidistant.
• - Ordinal responses have a numeric value.

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Question Type

• Example Ordinal response options in a
  closed-ended question
• When you turn off the frozen dairy dessert
  machine at the restaurants closing time, how
  frequently do you sanitize the dispenser?
• 1 Every time 4 Once a month
• 2 Every other time 5 Less than once a
  month
• 3 Once a week

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Question Type

• Likert scales contain pre-coded ordinal
  responses with assigned values. You can then
  calculate averages to determine the most
  prevalent response.
• Example Please rate the severity of your
  abdominal cramp pain (circle one)
• 1 minimal 3 moderate 5 very painful
• 2 mild 4 painful

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Question TypeLikert Scales
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Question TypeLikert Scales

• Example Please rate the severity of your
  abdominal cramp pain
• 1 minimal 3 moderate 5 very painful
• 2 mild 4 painful
• Calculate the average of responses, where N
  35
• 1 10 people 2 5 people 3 20 people
• 4 0 5 0
• 10 x 1 10 2 x 5 10 3 x 20 60
• 10 10 60 80
• 80 / 35 people 2.29 (average response of mild
  pain)

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Question Type

• Using Dont Know or Not Applicable
• When you have categorical, dichotomous response
  options such as, Yes and No, you may
  sometimes choose to add a Dont Know option.

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Skip Patterns

• 1a. Did you travel outside of River City during
  the week of June 10th through June 17th, 2005?
• Yes
• No
• Skip 1b and 1c if answer to 1a is No.
• 1b. To where did you travel? _____________
• 1c. What mode of transportation did you use?
• Airplane
• Automobile
• Chartered bus
• Cruise ship
• Train

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Open-ended Questions
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Open-ended Questions

• Allow respondents to provide answers in their own
  words.
• Yield qualitative data.
• May yield unanticipated answers that contribute
  to the study.
• Are most appropriate for hypothesis generating
  versus testing questionnaires.

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Question Type

• Example Open-ended questions
• What restaurants did you patronize in the past
  seven days?
• Please list the two main symptoms you are having
  with this illness

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Fill-in-the-blank Questions
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Fill-in-the-blank Questions

• Allow respondents to provide short answers in
  their own words.
• Yield qualitative data.
• Are most appropriate when possible response
  categories are too numerous to list.
• Are most appropriate when the question is
  measuring respondent characteristics versus
  attitudes, beliefs, or behaviors.

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Question Type

• Example Fill-in-the-blank Questions
• 1. County of residence _____
• 2. Age in years ____
• 3. Number of children under age 18 living in
  your household ____

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Question and AnswerOpportunity
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5 minute break
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Questionnaire Format
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Questionnaire Format

• We will now consider layout guidelines
• In general
• For interviewer administered questionnaires
• For self-administered questionnaires

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General Formatting Guidelines
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General Guidelines

• A well-designed questionnaire
• Minimizes respondent burden
• Minimal time to think about each response
• Minimal time to complete entire survey

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General GuidelinesRespondent Perspective

• Format page layout with a vertical flow from
  question to question and from response option to
  response option.
• Maintain white space on the page.
• Number every question.

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General GuidelinesRespondent Perspective

• Use consistent codes for response options.
• Arrange questions in a logical order even within
  sub-sections if possible.
• Use differentiating font for questions and
  response options.

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General GuidelinesRespondent Perspective

• Provide clear but brief instructions for survey
  completion.
• Indicate units for fill-in-the-blank questions.
• Use clear cues (text or arrows) to guide
  respondents through skip patterns.
• Use transitional cues for each subsection of
  questions (The next series of questions will
  ask about . . . ).

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General GuidelinesResearcher Perspective

• Include unique record identification numbers so
  you can maintain confidentiality and link data
  when applicable (e.g., in Epi Info).
• Use numbers versus check boxes for coded response
  options so they can be used for data entry and
  analysis (e.g., in Epi Info).

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General GuidelinesResearcher Perspective

• To reduce the difficulty of distinguishing
  between missing data and simply all no
  responses to a categorical list of response
  options, consider alternative formatting.
• Example standard question format
• Where did you see published information about
  this free HIV screening?
• Billboard on subway
• Doctors office
• Local newspaper

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General GuidelinesResearcher Perspective

• Example alternative question format
• Where did you see published information about
  this free HIV screening?
• Billboard on subway Yes No
• Doctors office Yes No
• Local newspaper Yes No

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Format Guidelines

• Interviewer versus
• Self-Administered Questionnaires

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Format Guidelines
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Supporting DocumentationInterviewers Manual

• Background
• Fieldwork
• Interviewing Techniques
• Telephone Interviewer Instructions (if
  applicable)
• Terms and Definitions
• Details of the Questionnaire
• Description of the Survey Area

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Supporting Documentation

• Standard format for interviewer introductions
  for telephone or face-to-face interviews
• Interviewers name
• Health department (or organization) represented
• One sentence description of the surveys purpose
  (e.g., There has been an outbreak of disease X
  in your county and we are calling you to . . .)
• A conservative estimate of how long the interview
  will take

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You are not finished yet. . .

Pilot Test Questionnaires!
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Pilot Test Questionnaires

• Are questions yielding the information that they
  are supposed to yield?
• Do respondents understand all wording?
• Do respondents interpret the questions the same
  way?
• Do closed-ended questions have a response option
  that applies to each respondent?
• Are skip patterns followed correctly?

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Case Study Example Interviewer
AdministeredQuestionnaire
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NC Rapid Needs Assessment Hurricane Isabel,
September 2003
Injury and Violence Prevention Branch, NC-DHHS DPH
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Who was involved in developing the RNA
Questionnaire?

• Epidemiology Section
• Public Health Preparedness Response
• Injury and Violence Prevention Branch
• Division of Environmental Health
• Division of Mental Health
• CDC specialists in mass trauma surveillance
• PHRST members

Injury and Violence Prevention Branch, NC-DHHS DPH
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Strategies for Designing the RNA Questionnaire

• Selected a TEAM leader
• Identified examples to serve as prototypes
• Agreed upon goals of data collection

Injury and Violence Prevention Branch, NC-DHHS DPH
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Strategies for Designing the RNA Questionnaire

• Limit forms to one-page
• Number all questions
• Preference for closed-ended questions
• Omit extremely sensitive questions
• Allow for Dont Know as a legitimate answer

Injury and Violence Prevention Branch, NC-DHHS DPH
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How many forms were needed?

• 1. Tracking Form
• 2. Survey Form
• 3. Referral Form

Injury and Prevention Branch, NC-DHHS DPH
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Tracking Form
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Respondent Referral Form
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Survey Instrument
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What data needed to be collected for Hurricane
Isabel?

• The SURVEY FORM
• Damage to homes
• Availability of usable utilities
• Incidence of hurricane related illness / injury
• Access to medical care
• Access to food and water
• Self-identified immediate needs

Injury and Violence Prevention Branch, NC-DHHS DPH
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Survey Instrument

• Header
• Date
• Interviewer
• Sampling information
• Respondent information

Injury and Violence Prevention Branch, NC-DHHS DPH
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Survey Instrument

• Household information
• Type
• Usual number of residents
• Residents during the storm
• persons at increased risk

Injury and Violence Prevention Branch, NC-DHHS DPH
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Survey Instrument

• Damage to house from the hurricane
• Habitability of structure
• Tarp needed
• Amount of flood water in the house
• Missing amount of mud or debris

Injury and Violence Prevention Branch, NC-DHHS DPH
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Survey Instrument

• Current status of household utilities
• Running water
• Power
• Toilet
• Telephone
• Radio
• Use of generator
• Use of charcoal

Injury and Violence Prevention Branch, NC-DHHS DPH
107
What else was needed?

• Question by Question instructions
• Standard in formal epidemiologic research
• Often only form of procedure manual when
  preparation time limited
• Often deciding factor in complicated analysis
• Introductory script
• English and Spanish

Injury and Violence Prevention Branch, NC-DHHS DPH
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Scripting English Introductory Script
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Lessons Learned
Injury and Violence Prevention Branch, NC-DHHS DPH
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Lessons Learned

• Include representative from a minority community
  during questionnaire development

Injury and Violence Prevention Branch, NC-DHHS DPH
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Lessons Learned

• Include question on the presence of mud or debris
  in survey questionnaire
• Appropriate for mountains and flatlands

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Lessons Learned

• Discuss at outset need for including questions on
  current conditions and risk factors for potential
  problems
• Landslides often occur days after hurricane
• Floods often occur days or weeks after event

Injury and Violence Prevention Branch, NC-DHHS DPH
113
Lessons Learned

• Emotional / mental stress is frequent after mass
  trauma how to craft questions that will
  identify stress that is not easily abated
• e.g., death of family member(s)

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5 minute break
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Guest Lecturer

• Aaron Wendelboe, MSPH
• NC Center for Public Health Preparedness

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Lessons Learned in Questionnaire Design

• Household Transmission of Pertussis Study

August 2005
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Overview

• Describe transmission of pertussis study
• Describe thought process in designing
  questionnaire
• Highlight weaknesses in questionnaire
• Highlight lessons learned from other studies

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Transmission of Pertussis Study Background

• International, multi-site study
• Determine who transmits pertussis to young
  infants
• Enroll infants 6 months of age diagnosed with
  pertussis
• Enroll family members and other close contacts

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Questionnaire DesignConsiderations
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Designing the Questionnaire

• Target Interviewees
• Infant index cases
• Adult household contacts
• Child household contacts
• Non-household contacts
• Data Collected
• Demographics, clinical history, biologic specimens

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Designing the Questionnaire

• Mode of administration?
• Self vs. Interviewer administered
• Training of interviewers?
• One long questionnaire or 4 separate
  questionnaires?
• One database or 4 separate databases?

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Ordering the Questions

• How to order the questions
• Meet research objective
• Ease of data entry
• Always start with inclusion / exclusion criteria
• Infants less 6 months of age what does this
  mean? (i.e., 6 months and 30 days?)

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Ordering the Questions

• Demographics
• Beginning or end
• Sensitive questions at end
• Build rapport
• Do not end with complicated questions

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Peer Review and Pilot Test

• Have colleagues review for
• Errors
• Clarity
• Improvement
• 10 pairs of eyes may have looked it over, but
  dont assume its enough . . .
• Pilot test among the target population
• May not be possible to pilot in real situation,
  but try to simulate as much as possible

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Lessons Learned
126

• Whats wrong with this question?
• Not all inclusive (1-1.9 hours?)
• Did not discriminate well almost everyone 5
  hours of contact
• Bad question or bad training of interviewers?

127

• Ambiguous question for children less than 4 years
  of age
• Primary series given at 2, 4, and 6 months
• 1st booster given at 18 months
• Adolescent booster uncommon
• Better if followed with If yes, did you
  participate in a vaccine trial?

128

• Index questionnaire didnt ask this question
• Not detailed enough
• IRB conflict?
• Ambiguous study nurses didnt know how to
  answer this question

129
Consistency Across Questionnaires

• Non-household contacts
• Population included both adults and children
• Only had one form designed for adults

130
Site-Specific Opinions

• Get input from study team, especially those
  collecting the data
• French and Houston investigators wanted to
  collect additional pieces of data
• Tuberculosis study in South Africa
• Personnel who collected data changed
  questionnaire without notifying principal
  investigator

131
People Can Make the Difference

• Pittsburgh started strong quality decreased
  with new staff
• Houston great at recruiting contacts (both
  household and non-household)
• Rapport, incentives, etc.
• France great at follow-up with second visit

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Beyond Pertussis. . .

• Salmonella outbreak
• Intro paragraph
• Too long
• Just to review questions
• Too redundant
• I dont know option
• Important to allow for all possible responses
• People dont like to appear ignorant

133
Summary of Lessons Learned

• Interviewer training
• Pilot testing
• Application of skip patterns
• Clear questions asked of participants
• Unambiguous questions to collect detailed
  information
• Consistency in data collection
• Research team input

134
Question AnswerOpportunity
135
Session IV Summary
136
Session Summary

• With an understanding of good questionnaire
  design principles, you will ask only about what
  you need to meet your research objectives.
• In preparation for questionnaire design, you
  should have clear research objectives list
  variables to be measured identify an analysis
  plan and consider cost and logistical aspects.

137
Session Summary

• Use a hypothesis generating questionnaire to
  explore all potential sources of infection, but
  with a small number of cases and no comparison
  group.
• A hypothesis testing questionnaire literally
  tests a research hypothesis based on data
  collected via a hypothesis generating
  questionnaire. Include both cases and controls in
  the survey sample population.

138
Session Summary

• The three broad question types are
  closed-ended open-ended and fill-in-the-blank.
  You may use only one or a combination of all,
  depending on the purpose of your survey.
• Key elements of question design are
  reliability validity specificity simplicity
  asking only one question mutually exclusive
  answer choices providing date / time references
  and using response options that parallel existing
  data sources.

139
Session Summary

• A well-formatted questionnaire minimizes
  respondent burden by using question order,
  spacing, distinctive font, symbols, and simple,
  short instructions to facilitate navigation and
  using customized components for interviewer
  administered versus self-administered settings.
• Question type and response option formatting
  impact how you can manage and analyze your data.

140
Next Session October 6th100 p.m. 300 p.m.

• Topic Interviewing Techniques

141
References and Resources

• American Statistical Association (1999). What Is
  a Survey? Designing a Questionnaire. Alexandria,
  VA Section on Survey Research Methods.
• American Statistical Association (1997). What Is
  a Survey? More About Mail Surveys. Alexandria,
  VA Section on Survey Research Methods, American
  Statistical Association.
• Centers for Disease Control and Prevention, Food
  borne and Diarrheal Diseases Branch, Food borne
  Outbreak Response and Surveillance Unit (2003).
  Outbreak Investigation Toolkit Standard
  Questionnaire. Online resource
  http//www.cdc.gov/foodborneoutbreaks/standard_que
  stionnaire.htm
• Data Skills Online web site, Office of
  Continuing Education, Institute for Public
  Health, UNC Chapel Hill.
• An Overview of Primary Data Collection
  Instruments and Designing Questionnaires
  online self-instructional tools.
  http//www.sph.unc.edu/toolbox/.

142
References and Resources

• Centers for Disease Control and Prevention.
  Standard Food Borne Disease Outbreak
  Questionnaire. (PDF file) at http//www.cdc.gov/f
  oodborneoutbreaks/question/standard_questionnaire.
  pdf
• Centers for Disease Control and Prevention (CDC).
  2005. Behavioral Risk Factor Surveillance System
  Survey Questionnaire. Atlanta, Georgia U.S.
  Department of Health and Human Services, Centers
  for Disease Control and Prevention.
• Fowler, F.J. (1993). Survey Research Methods
  Second Edition. Sage Publications Newbury
  Park.

143
References and Resources

• Reingold, A. (1998). Outbreak Investigations A
  Perspective. Emerging Infectious Diseases. Vol.
  4 No. 1 January March 1998.
• Salant, P. and Dillman, D. (1994). How to
  Conduct Your Own Survey. John Wiley Sons,
  Inc. New York.
• Stehr-Green, J.K. (2002). A Multi-state Outbreak
  of E. coli 0157H7 Infection Case Study
  Instructors Guide. Atlanta, GA U.S. Department
  of Health and Human Services, Public Health
  Service, Centers for Disease Control and
  Prevention. http//www.phppo.cdc.gov/phtn/casestud
  ies/classroom/ecoli.htm

144
References and Resources

• Stehr-Green, J. and Stehr-Green, P. (2004).
  Hypothesis Generating Interviews. Module 3 of a
  Field Epidemiology Methods course being developed
  in the NC Center for Public Health Preparedness,
  UNC Chapel Hill.
• Torok, M. (2004). FOCUS on Field Epidemiology.
  Case Finding and Line Listing A Guide for
  Investigators. Volume 1, Issue 4. NC Center for
  Public Health Preparedness.
• Wiggins, B. and Deeb-Sossa, N. (2000).
  Conducting Telephone Surveys. Chapel Hill, NC
  Odum Institute for Research in Social Science.