Next: , Previous: Dealing with suspicious data, Up: Data Screening and Transformation


5.2.3 Inverting negatively coded variables

Data entry errors are not the only reason for wanting to recode data. The sample file hotel.sav comprises data gathered from a customer satisfaction survey of clients at a particular hotel. In reliability, this file is loaded for analysis. The line display dictionary. tells pspp to display the variables and associated data. The output from this command has been omitted from the example for the sake of clarity, but you will notice that each of the variables v1, v2 ... v5 are measured on a 5 point Likert scale, with 1 meaning “Strongly disagree” and 5 meaning “Strongly agree”. Whilst variables v1, v2 and v4 record responses to a positively posed question, variables v3 and v5 are responses to negatively worded questions. In order to perform meaningful analysis, we need to recode the variables so that they all measure in the same direction. We could use the RECODE command, with syntax such as:

     recode v3 (1 = 5) (2 = 4) (4 = 2) (5 = 1).

However an easier and more elegant way uses the COMPUTE command (see COMPUTE). Since the variables are Likert variables in the range (1 ... 5), subtracting their value from 6 has the effect of inverting them:

     compute var = 6 - var.

reliability uses this technique to recode the variables v3 and v5. After applying COMPUTE for both variables, all subsequent commands will use the inverted values.