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Compute
Function
(recoding)
Task: Using the Computer Function to recode a
reverse coded item.
Start off by importing the
ex3reverse.sav
into the Data Editor window of PASW / SPSS (from this point forward
referred to as simply SPSS).
The compute function can be used to recode a
Likert scale item which was initial reverse coded by the wording of its
stem or statement. The keys to using compute to recode an item are two
simple formulas. The general idea is that we add 1 to the number of
possible response choices, creating a constant, and then subtract the
old value from that constant.
Formula (1): k + 1 = C
where k equals the number
of possible Likert response choices and C
equals the Constant we will apply in the compute function.
Formula (2): C - O
= RC
where C equals the Constant
from the previous equation, O equals the old
variable values, and RC equals the newly recoded
variable values.
For instance, our current example uses a 5-point
Likert response format. Since we want to reverse the numeric coding in
our data file, we add 1 to 5 and get 6 as our constant.
(1): 5 + 1 = 6
We then subtract each person's response on the old
variable from 6 and the result will be each person's recoded response.
(2): 6 - q4 = q4_RC
For the example below, we will be recoding
question 4 (q4) as was done using the Recode function in a previous
module (Module
4.3). If you would like a more detailed description of our
example data and the fictional situation behind it, please review that
module.
To use the Compute function, simply go to
"Transform", "Compute Variable..."
You should now see the "Compute Variable" dialog
box.
In the Compute dialog, first type q4_RC in the
"Target Variable:" box which will be the name of our new variable.
Then, type our constant (C) of 6 in the "Numeric
Expression:" box, followed by a space, then a minus sign, then a space.
Next, highlight and move q4 from the available variables box to the
"Numeric Expression:" box using the arrow. Now click on "OK" or "Paste"
if you would prefer a syntax record be created (from which you can
highlight and submit the syntax to perform the compute/recode).
That concludes using the Compute function to
recode an item.
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