Data Coding

1. Data Coding

2. What is it?? • “Coding is the translation of data into labeled categories suitable for computer processing” –Richardson, Meyburg and Ampt 1995

3. How do we do that?? • Distinguish between nominal, ordinal, interval and ratio data to code • What is nominal data? • Has no order. Example- male (1) female (2) • What is ordinal data? • Has order but the interval between data has no meaning. Example- Priority ranking of mode of transportation • What is interval data? • Has order and meaning between the data, but no starting point. Example- Year of birth of respondent, or times of start/end of activities in time use diary • What is ratio data? • Has order, meaning between data and a distinct starting point. Example- distance of trips, age of respondent (can be obtained from interval data i.e. year of birth to yield age)

4. What’s Next??? • When devising a coding scheme, think about how the data will be used computationally in the analysis • Think about each question asked, why you asked the question and what data you want to get from the answer.

5. Before you start coding • It is necessary to make sure that each respondent has their own code • Label everything with the unique identifier for each respondent… the envelopes, diary and the questionnaire!!!!!

6. Class Assignment • Devise a code book for your group’s survey. This consists of two things: • The definition of coding categories to be used • The methods to be used in allocating individuals answers to these categories • Each question will have a coding frame (the allocation of answers to codes) which together comprise the code book

7. Code Categories • In selecting coding categories, it is wise to use categories that have been used in previous surveys like the census or transportation surveys with which you might make comparisons later on (or just for extra guidance). Do a little research! • For each question, the coding frame should consist of mutually exclusive and exhaustive categories so that every possible answer will fit into one and only one category.

8. Odds and Ends for Groups • Stay consistent in the coding book. For example, all yes/no questions should have the same coding scheme. • Devise a scheme for instances where the question was left blank, the respondent didn’t know the answer, the question wasn’t applicable, etc.

9. Odds and Ends cont. • It is your job to look at the data that you have gathered, come up with a code book and address problems that arise with a viable solution. There will be problems! • Try your codes out. Select a few surveys and try to code them. Does your group’s code book work???

10. Dealing with the “other” response • The trade offs • It’s always possible to aggregate the other responses to more general categories, but impossible to disaggregate general categories to more specific • However, a long list of categories with minimal differences lead to coder bias and unreliable results

11. Example • Oregon DOT code book example • https://scholarsbank.uoregon.edu/dspace/bitstream/1794/1232/1/TRANS4+Codebook.pdf • Look at this example. Not all of it will make sense, that’s ok! Ours will be a little bit more simple. • Include the question, measurement level (nominal etc.), value and label

12. For today • Finish your thank you letters. Don’t sign it specifically, sign it from the entire class. We will use names where we can. • Come up with a list of names of people you gave your surveys to • Label the surveys you have received already!!! • Start working on code books