Sunday, January 30, 2011

Topic 6 : Coding & Cleaning Survey Data



Data Preparation Steps

-          Interviewing / self completion
-          Receiving completed questionnaires
-          Validating
-          Checking and editing
-          Coding
-          Data entry
-          Verifying

Processing Paper Questionnaire

-          Control register
-          Outcome
o   Completed interview
o   Refusal
o   Did not speak English
o   Ineligible
o   No contact
o   In phone surveys: dead number / fax / engaged
-          Questionnaire identification

Validating

-          Determining when questionnaire is suitable to be included in analysis
o   Right person completed
o   Was interview conducted the right way
§  Validate 10%
§  Monitor real time
§  Call back

Checking & Editing

-          Editing – visual check – acceptable for data processing
-          Issues
o   Incomplete / pages missing
o   Pattern of responses may show respondent did not understand instructions / not followed correctly
o   Responses may show little variance, eg – all questions rated 4 on likert scale
-          Actions
o   Check filter / skip / branch questions have been followed
o   All relevant questions followed
o   Deal with incomplete questionnaires
o   Real with irregularities, ie, aged 13 with Phd
è Create new response category : information not provided
è Best guess

Coding

-          Pre-coded vs open ended
-          Open ended may be coded by researcher
-          Expand other category
-          Codebook
o   Exact question
o   Variable name
o   Data type
o   Explanation of valid codes
o   Definition of missing values
o   Special instructions
-          Issues in coding
o   More codes, greater detail
o   Fewer codes, easier analysis
-          How to code an open response question
-          How to code demographic questions
-          Coding others
-          Data entry

Verification

-          Setting data entry controls
-          Manually scanning data
-          Re-entry
-          Computer based verification
-          Changing data values (version control)




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