Missing values in numeric fields
The term missing values refers to data in numeric fields that is either non-numeric or totally blank. You might find them in data gathered from questions of the type shown below:
1. Have you ever rented a video?
Yes, have rented a video ........ 1 (8)
No, have not rented a video ..... 2 (GOTO Q.3)
Not answered .................... & (GOTO Q.3)
2. How many videos have you rented in the last month?
____________________ (9 - 10)
3. ......... continue with questionnaire |
If the respondent replies ‘no’ to question 1 or does not answer it at all, question 2 is not asked and columns 9 and 10 are left blank. If the respondent replies ‘yes’ to question 1 then question 2 should be coded either with a numeric value or, perhaps, with && for a don’t know answer. The blank data and && are missing values.
You might also find missing values when a numeric field is incorrectly coded with a combination of numbers and letters. This is usually the result of mistyping when the data is entered and can often be corrected by looking at the questionnaire itself and then cleaning the data within the edit section of the run.
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