Title: Class 9 Interpreting Pretest Data, Considerations in Modifying or Adapting Measures November 13, 200
1Class 9 Interpreting Pretest Data,
Considerations in Modifying or Adapting Measures
November 13, 2008
- Anita L. Stewart
- Institute for Health Aging
- University of California, San Francisco
2Overview of Class 9
- Analyzing pretest data
- Modifying/adapting measures
- Keeping track of your study measures
- Creating and testing scales in your sample
3Summarize Data on Pretest Interviews
- Summarize problems and nature of problems for
each item - Determine how important problems are
- Results become basis for possible
revisions/adaptations
4Methods of Analysis
- Optimal transcripts of all pretest interviews
- For each item - summarize all problems
- Analyze dialogue (narrative) for clues to solve
problems
5Behavioral Coding
- Systematic approach to identifying problems with
items - interviewer and respondent problems
- Can code problems based on
- Standard administration
- Responses to specific probes
6Examples of Interviewer Behaviors Indicating
Problem Items
- Question misread or altered
- Slight change meaning not affected
- Major change alters meaning
- Question skipped
7Examples of Respondent Behaviors Indicating
Problem Items
- Asks for clarification or repeat of question
- Did not understand question
- Doesnt know the answer
- Qualified answer (e.g., it depends)
- Indicates answer falls between existing response
choices - Refusal
8Summarize Behavioral Coding For Each Item
- Proportion of interviews (respondents) with each
problematic behavior - of occurrences of problem divided by N
- 7/48 respondents requested clarification
9Behavioral Coding Summary Sheet Standard
Administration (N20)
10Can Identify Problems Even When No Problem
Behaviors Found
- Respondents appear to answer question
appropriately - Additional problems identified with probes
- Probe on meaning Response indicates lack of
understanding - Probe on use of response options Response
indicates options are problematic
11Behavioral Coding of Probe Results
- I asked you how often doctors asked you about
your health beliefs. What does the term health
beliefs mean to you? - Behavioral coding times response indicated
lack of understanding as intended - e.g., 2/15 respondents did not understand meaning
based on response to probe
12Behavioral Coding Summary Standard
Administration (N20) Probes (N10)
13Interpret Behavioral Coding Results
- Determine if problems are common
- Items with only a few problems may be fine
- Quantifying common problems
- several types of problems (many row entries)
- several subjects experienced a problem
- problem w/item identified in gt15 of interviews
14Continue Analyzing Items with Common Problems
- Identify serious common problems
- Gross misunderstanding of the question
- Yields completely erroneous answer
- Couldnt answer the question at all
- Some less serious problems can be addressed by
improved instructions or a slight modification -
15Addressing More Serious Problems
- Conduct content analysis of transcript
- Use qualitative analysis software (e.g., NVIVO)
- For these items review dialogue that ensued
during administration of item and probes - can reveal source of problems
- can help in deciding whether to keep, modify or
drop items
16Results Probing Meaning of Phrase
- I asked you how often doctors asked you about
your health beliefs? What does the term health
beliefs mean to you? - .. I dont want medicine
- .. How I feel, if I was exercising
- .. Like religion? --not believing in
going to doctors?
17Results Probing Meaning of a Phrase
- What does the phrase office staff mean to you?
- the receptionist and the nurses
- nurses and appointment people
- the person who takes your blood
pressure and the clerk in the front office
18Results Probing Meaning of Phrase
- On about how many of the past 7 days did you eat
foods that are high in fiber, like whole grains,
raw fruits, and raw vegetables? - Probe what does the term high fiber mean to
you? - Behavioral coding of item
- Over half of respondents exhibited a problem
- Review answers to probe
- Over ΒΌ did not understand the term
Blixt S et al., Proceedings of section on survey
research methods,American Statistical
Association, 19931442.
19Results No Behavior Coding Issues but Probe
Detected Problems
- I seem to get sick a little easier than other
people (definitely true, mostly true, mostly
false, definitely false) - Behavioral coding of item
- Very few problems
- Review answers to probe
- Almost 3/4 had comprehension problems
- Most problems around term mostly (either its
true or its not)
Blixt S et al., Proceedings of section on survey
research methods,American Statistical
Association, 19931442.
20Results Beck Depression Inventory (BDI) and
Literacy
- Cognitive interviews older adults, oncology pts,
and less educated adults - Administered REALM (reading literacy test) and
some selected BDI items - Asked to paraphrase items
TL Sentell, Community Mental Health Journal,
200839323
21Results Beck Depression Inventory (BDI) and
Literacy (cont)
- For each item, from 0-62 correctly paraphrased
item - Most misunderstandings vocabulary confusion
- Phrase I am critical of myself for my weaknesses
and mistakes - Critical is when youre very sick
- I dont know how to explain mistakes
22Interpreting Pretest Results of Self-Administered
Questionnaires
- Missing data is a clue to problematic items
- More missing data associated with unclear,
difficult, or irrelevant items - Cognitive interviewing can help determine reasons
for missing data
23How Missing Data Prevalence Helps
- Items with large percent of responses missing
clue to problem - In H-CAHPS pretest
- Did hospital staff talk with you about whether
you would have the help you needed when you left
the hospital? - 35 missing for Spanish group
- 29 missing for English group
MP Hurtado et al. Health Serv Res, 200540-6,
Part II2140-2161
24Exploring Differences by Diverse Groups
- Back to issue of equivalence of meaning across
groups - All cognitive interview analyses can be done
separately by group
25Results Use of Response Scale
- Do diverse groups use the response scale in
similar ways? - Re questions about cultural competence of
providers - Interviewers reported that Asian respondents who
were completely satisfied did not like to use the
highest score on the rating scale
California Pan-Ethnic Health Network (CPEHN)
Report, 2001
26Results Use of Response Scale (cont)
- Behavioral Risk Factor Surveillance Survey
(BRFSS) pretesting - Found that Puerto Rican, Mexican American, and
African American respondents more likely to
choose extreme response categories than Whites.
RB Warnecke et al, Ann Epidemiol, 19977334-342
27Differential Use of CAHPS 0-10 Global Rating
Scale
- Compared Medicaid and commercially insured adults
on use of scale - Medicaid enrollees more likely than commercial
participants to use extreme ends of scale - All other things being equal
PC Damiano et al, Health Serv Outcomes Res
Method, 20045193-205
28Results Probe on DifficultyCES-D Item
- During the past week, how often have you felt
that you could not shake off the blues, even with
help from family and friends - Probe Do you feel this is a question that people
would or would not have difficulty understanding? - Latinos more likely than other groups to report
people would have difficulty
TP Johnson, Health Survey Research Methods, 1996
29Overview of Class 9
- Analyzing pretest data
- Modifying/adapting measures
- Keeping track of your study measures
- Creating and testing scales in your sample
30Now What!
- Issues in adapting measures based on pretest
results - Cognitive interview pretesting during development
phases of measure - Can modify items and continue pretesting
- Cognitive interview pretesting prior to using
published survey - More problematic
31Modification Probing the Meaning of a Phrase
- What does the phrase office staff mean to you?
- the receptionist and the nurses
- nurses and appointment people
- the person who takes your blood
pressure and the clerk in the front
office - We changed the question to receptionist and
appointment staff
32Results Probing Meaning and Cultural
Appropriateness
- I asked you how often doctors asked you about
your health beliefs? What does the term health
beliefs mean to you? - .. I dont want medicine
- .. How I feel, if I was exercising
- .. Like religion? --not believing in
going to doctors? - We changed the question to personal beliefs
about your health
33Criteria for Whether or Not to Modify Measure
- Contact author
- May be open to modifications, working with you
- Be sure your opinion is based on extensive
pretests with consistent problems - Dont rely on a few comments in a small pretest
- Work with a measurement specialist to assure that
proposed modifications are likely to solve problem
34Tradeoffs of Using Adapted Measures
- Advantages
- Improve internal validity
- Disadvantages
- Lose external validity
- Know less about modified measure
- Need to defend new measure
35Adding New (Modified) Items
- One approach if you find serious problems with a
standard measure - Write new items you think will be better (use
same format) - Retain original intact items and add modified
items - Can test original scale and revised scale with
modified items instead of original items
36Modifying response categories
- If response choices are too few and/or coarse,
can improve without compromising too much - Try adding levels within existing response scale
37One Modification Too Many Response Choices
- SF36 version 1
- 1 - All of the time
- 2 - Most of the time
- 3 - A good bit of the time
- 4 - Some of the time
- 5 - A little of the time
- 6 - None of the time
- SF36 version 2
- 1 - All of the time
- 2 - Most of the time
- 3 - Some of the time
- 4 - A little of the time
- 5 - None of the time
38Modification of Health Perceptions Response
Choices for Thai Translation
- Usual responses
- 1 - Definitely true
- 2 - Mostly true
- 3 - Dont know
- 4 - Mostly false
- 5 - Definitely false
- Modified
- 1 Not at all true
- 2 A little true
- 3 - Somewhat true
- 4 - Mostly true
- 5 Definitely true
e.g., My health is excellent, I expect my health
to get worse
39Modifying Item Stems
- If item wording will not be clear to your
population - Can add parenthetical phrases
- Have you ever been told by a doctor that you have
diabetes (high blood sugar)?
40Strategy for Modified Measures
- Test measure in original and adapted form
- Choose measure that performs the best
41Analyzing New (Modified) Measure
- Factor analysis
- All original items
- Original plus new items replacing original
- Correlations with other variables
- Does the new measure detect stronger
associations? - Outcome measure
- Does the new measure detect more change over
time?
42Analytic Strategy CAHPS 0-10 Global Rating
Scale Response
Cant change the scale part of standardized
survey
- Usual classifications
- 0-9, 10 (dichotomy)
- Proposed classification
- 0-8, 9-10
PC Damiano et al, Health Serv Outcomes Res
Method, 20045193-205
43Overview of Class 9
- Analyzing pretest data
- Modifying/adapting measures
- Keeping track of your study measures
- Creating and testing scales in your sample
44Questionnaire Guides
- Organizing your survey measures
- Keep track of measurement decisions
- Sample guide to measures (last week)
- Documents sources of measures
- Any modifications, reason for modification
45Sample Guide to Measures Handout
- Type of variable
- Concept
- Measure
- Data source
- Number of items/survey question numbers
- Number of scores or scales for each measure
- References
46Sample Summary of Survey Variables.. Handout
- Develop codebook of scoring rules
- Several purposes
- Variable list
- Meaning of scores (direction of high score)
- Special coding
- How missing data handled
- Type of variable (helps in analyses)
47Item Naming Conventions
- Optimal coding is to assign raw items their
questionnaire number - Can always link back to questionnaire easily
- Some people assign a variable name to the
questionnaire item - This will drive you crazy
48Variable Naming Conventions
- Assigning variable names is an important step
- make them as meaningful as possible
- plan them for all questionnaires at the beginning
- For study with more than one source of data, a
suffix can indicate which point in time and which
questionnaire - B for baseline, 6 for 6-month, Y for one year
- M for medical history, L for lab tests
49Variable Naming Conventions (cont)
- Medical History Questionnaire
- HYPERTMB HYPERTM6
- Baseline 6 months
50Variable Naming Conventions (cont)
- A prefix can help sort variable groupings
alphabetically - e.g., S for symptoms
- SPAINB, SFATIGB, SSOBB
-
51Overview of Class 9
- Analyzing pretest data
- Modifying/adapting measures
- Keeping track of your study measures
- Creating and testing scales in your sample
52On to Your Field Test or Study
- What to do once you have your baseline data
- How to create summated scale scores
53Preparing Surveys for Data Entry 4 Steps
- Review surveys for data quality
- Reclaim missing and ambiguous data
- Address ambiguities in the questionnaire prior to
data entry - Code open-ended items
54Review Surveys for Data Quality
- Examine each survey in detail as soon as it is
returned, and mark any.. - Missing data
- Inconsistent or ambiguous answers
- Skip patterns that were not followed
55Reclaim Missing and Ambiguous Data
- Go over problems with respondent
- If survey returned in person, review then
- If mailed, call respondent ASAP, go over missing
and ambiguous answers - If you cannot reach by telephone, make a copy for
your files and mail back the survey with request
to clarify missing data
56Address Ambiguities in the Questionnaire Prior to
Data Entry
- When two choices are circled for one question,
randomly choose one (flip a coin) - Clarify entries that might not be clear to data
entry person
57Code Open-Ended Items
- Open-ended responses have no numeric code
- e.g., name of physician, reason for visiting
physician - Goal of coding open-ended items
- create meaningful categories from variety of
responses - minimize number of categories for better
interpretability - Assign a numeric score for data entry
58Example of Open-Ended Responses
- 1.What things do you think are important for
doctors at this clinic to do to give you high
quality care? - Listen to your patients more often
- Pay more attention to the patient
- Not to wait so long
- Be more caring toward the patient
- Not to have so many people at one time
- Spend more time with the patients
- Be more understanding
59Process of Coding Open-Ended Data
- Develop classification scheme
- Review responses from 25 or more questionnaires
- Begin a classification scheme
- Assign unique numeric codes to each category
- Maintain a list of codes and the verbatim answers
for each - Add new codes as new responses are identified
- If a response cannot be classified, assign a
unique code and address it later
60Example of Open-Ended Codes
- Communication 1
- Listen to your patients more often 1
- Pay more attention to the patient 1
- Access to care 2
- Not to wait so long 2
- Not to have so many people at one time 2
- Allow more time 3
- Spend more time with the patients 3
- Emotional Support 4
- Be more understanding 4
- Be more caring toward the patient
61Verify Assigned Codes
- Have a second person independently classify each
response using final codes - Investigator can review a small subset of
questionnaires to assure that coding assignment
criteria are clear and are being followed
62Reliability of Open-Ended Codes
- Depends on quality of question, of codes
assigned, and the training and supervision of
coders - Initial coder and second coder should be
concordant in over 90 of cases
63Data Entry
- Set up file
- Double entry of about 10 of surveys
- SAS or SPSS will compare two for accuracy
- Acceptable 0-5 error
- If 6 or greater consider re-entering data
64Print Frequencies of Each Item and Review Range
Checks
- Verify that responses for each item are within
acceptable range - Out of range values can be checked on original
questionnaire - corrected or considered missing
- Sometimes out of range values mean that an item
has been entered in the wrong column - a check on data entry quality
65Print Frequencies of Each Item and Review
Consistency Checking
- Determine that skip patterns were followed
- Number of responses within a skip pattern need to
equal number who answered skip in question
appropriately
66Print Frequencies of Each Item and Review
Consistency Checking (N90)
- 1. Did your doctor prescribe any medications?
(75 yes, 15 no) - 1a. If yes, did your doctor explain the side
effects of the medication? (80 responses) - Often will find that more people answered the
second question than were supposed to
67Print Frequencies of Each Item and Review
Consistency Checking (cont.)
- Go back to a questionnaires of those with
problems - check whether initial filter item was
incorrectly answered or whether respondent
inadvertently answered subset - sometimes you wont know which was correct
- Hopefully this was caught during initial review
of questionnaire and corrected by asking
respondent
68Deriving Scale Scores
- Create scores with computer algorithms in SAS,
SPSS, or other program - Review scores to detect programming errors
- Revise computer algorithms as needed
- Review final scores
69Creating Likert Scale Scores
- Translate codebook scoring rules into program
code (SAS, SPSS) - Reverse all items as specified
- Apply scoring rules
- Apply missing data rules
- Sample for SAS (see handout)
70Testing Scaling Properties and Reliability in
Your Sample for Multi-Item Scales
- Obtain item-scale correlations
- Part of internal consistency reliability program
- Calculate reliability in your sample (regardless
of known reliability in other studies) - internal-consistency for multi-item scales
- test-retest if you obtained it
71SAS Chapter 3 Assessing Reliability with
Coefficient Alpha
- Review statements and output
- How to test your scales for internal consistency
and appropriate item-scale correlations
72SAS/SPSS Both Make Item Convergence Analysis Easy
- Reliability programs provide
- Item-scale correlations corrected for overlap
- Internal consistency reliability (coefficient
alpha) - Reliability with each item removed
- To see effect of removing an item
73SAS Obtaining Item-Scale Correlations and
Coefficient Alpha
- PROC CORR
- DATAdata-set-name
- ALPHA
- NOMISS
- VAR (list of variables)
- Output
- Coefficient alpha
- Item correlations
- Item-scale correlations corrected for overlap
SAS Manual, Chapter 3 Assessing
ScaleReliability with Coefficient Alpha
74SAS Chapter 3 Assessing Scale Reliability with
Coefficient Alpha
- PROC CORR
- DATAdata-set-name
- ALPHA
- NOMISS
- VAR (list of variables)
- Output
- Coefficient alpha
- Item correlations
- Item-scale correlations corrected for overlap
75Testing Reliability in STATA
- www.stata.com/help.egi?alpha
- Alpha varlist if in , options
- SEE HANDOUT
76What if Reliability is Too Low?
- Have to decide if you need to modify a scale
- New scales under development
- Modify using item-scale criteria
- Standard scales cannot change
- Simply report problems as caveats in your
analyses - If problem is substantial
- Can create a modified scale and report results
using standard and modified scale
77Value of Pretesting Experts Say..
- evidence from our work suggests that many survey
questions are seriously underevaluated - Evaluating items at final pretest phase is often
too late in the process - Too late for extensive question redesign
- A series of question evaluation steps is needed
beginning well before the survey
FJ Fowler and CF Cannell. Using behavioral coding
to identify problems with survey questions. In
Answering Questions, eds N Schwarz et al,
Jossey-Bass, 1996
78Homework for Class 10
- Conduct 2 pretest interviews with individuals
similar to your target population - Administer all questions
- Administer your 4 probes
- Summarize briefly your pretest results
- Indicate whether the measure appears to be
appropriate for the 2 pretest subjects - No inferences to broader sample needed
.