Data Processing

• Data Processing 

  • systematic procedure to ensure that the information/data gathered are complete, consistent and suitable for analysis.
  • Data collection 
  • Data processing (coding, encoding, editing) 
  • Analysis
• Data collection : gathered from defined and accurate sources so that the subsequent findings are valid and usable
• data preparation : sorting and filtering raw data to remove unnecessary and inaccurate data
• data input : converted into machine readable form and fed into the processing unit
• data processing : subjected to various methods to generate a desirable output
• data interpretation : transmitted and displayed to the user in a readable form
• data storage : stored for further use
• • Manual - without using any machine or tool to get the required results
• • Mechanical - uses typewriters or mechanical printers
• • Electronic - uses computers softwares such as MS Excel, SPSS to collect and summarize data
• • Field Code: actual value or information given by the respondent
• • Bracket Code: recorded as range of values rather than actual values
• • Factual Code: codes are assigned to a list of categories of a given variable
• • Pattern Code: applicable for questions with multiple responses
• set the Rules For Code Construction - coding categories should be exhaustive or mutually exclusive and independent
• Pre-Coding Fixed-Alternative Questions (FAQs) - writing codes for FAQs on the questionnaire before the data collection

  1. coding Open-Ended Questions
  2. 3-stage process: (1) Perform a test tabulation, (2) plan a coding scheme, (3) Code all responses
• Maintaining a Code Book - identifies each variable in a study, the variable's description, code name, and position in the data matrix 
• Producing Code - physical activity of transferring the data from the questionnaire or data collection form [to the computer] after the data has been collected
• Combining Editing and Coding - the coding and editing is combined for further analysis
• Rules in Code Construction 

  • Number of rules must be kept to minimum (<8)
  • Codes should be exhaustive and mutually exclusive
  • Adopt coding convention for questions with similar answers
• Coding Problems 

  • No response
  • Not applicable questions 
• Coding Manual 

  • A document which contains a record of all codes assigned to the responses to all questions in the data collection forms
  • Minimum information that must be included in a coding manual
  • Variable name
  • Variable description
  • Coding instructions
• Data Encoding 

  • Entering the data/responses in a spreadsheet
  • MS Excel
  • MS Access
  • Epi Info
• Data Editing 

  • process of examining and adjusting the data collected in questionnaires to detect errors and omissions, legibility, consistency and readying them for coding and storage
  • detects errors and omissions, corrects them when possible and certifies that minimum data quality standards are achieved
  • performed during data collection, encoding, before data analysis
• (1) Field Editing

  • done by enumerator or a field supervisor on the same data as the interview
  • reviewing the accomplished data collection forms
  • decoding of abbreviations or special symbols
  • making callbacks/messages for verification/clarification of incomplete answers
• (2) Central Editing

  • also known as in house editing
  • done by the researcher or a central office staff after getting all the questionnaires/forms from the enumerator or respondents
  • checking of inconsistencies and incorrect entries after receiving the questionnaire from the field
  • more rigorous than filed editing
  • checking of encoded data
• Importance of Data Editing 

  • Make corrections as early as possible
  • Reduce non-response or incomplete answers
  • Eliminate inconsistencies, incorrect information
  • Make the entries clear, legible and comprehensive
  • Ensure uniformity
  • Prepare data for analysis
• What to Check when editing Data? 

  • Check for duplicate entries
  • Check the totals of each variable if the same as with the sample size
  • For qualitative data, check if categories are consistent with what is specified in the coding manual
  • For quantitative data, check the minimum and maximum if they are logical given the possible values of variable
• Data Coding 

  • conversion of verbal/written information into numbers which can be more easily encoded, counted and tabulated
  • process of identifying, classifying and assigning each answers with some symbols (alphabetical or numerals) so that the responses can be recorded into a limited number of classes or categories