[R] Comparing a 4-point and 5-point Likert scale

[Jim Lemon]

On 06/03/2010 11:11 PM, Simon Kiss wrote:
> Help with survey data:
> Hello R colleagues,
> I hope this is an appropriate place to direct this question. It relates
> specifically to the comparability of a 5-point likert to a 4-point
> likert scale.
>
> One question in my dataset asks "How much should be done to reduce the
> gap between rich and poor"
> Much more, somewhat more, about the same, somewhat less and much less.
>
> The second questions ask:
> "People who can afford to, should be able to pay for their own health care"
> strongly agree, agree, disagree, strongly agree.
>
> Now, assuming that I rescale them so that 1 equals the most egalitarian
> position and the highest number (4 or 5) equals the least egalitarian
> position, how can I make these two results comparable.
>
> Two ways come to mind: one is to collapse both into a dichotomous
> variable and do a logistic regression on both. The danger here is that I
> have to decide what to do with the middle position in the first
> question, assign it to the egalitarian or non-egalitarian category.
> A second way would be to multiply the scores in the first question by 4
> (to get results that are either 4, 8, 12, 16 or 20) and then multiply
> the second question by five to get responses that are either 5, 10, 15
> or 20. My idea is then to add the two, average them and use that value
> as an index of economic egalitarianism?
> Yes / no? Suggestions?
> I am an R user and I hope that a purely statistical question is not
> especially misplaced.

Hi Simon,
Strictly speaking, only the second question is a Likert scale, as that 
assumes a measure of agreement, not some other quantitative dimension. 
Assuming that the fourth option on Q2 is "Strongly disagree", and you 
wish to argue that this and the first option on Q1 ("Much more") both 
represent the maximally egalitarian responses, you could reverse Q2
and scale it to the same range (i.e. 1,2,3,4,to 5,3.67,2.33,1) so that 
it would have the same weight in an additive composite score. If I was 
reviewing a paper that suggested this, I would expect a pretty sound 
defense of the notion that income redistribution and public health care 
were strongly linked attitudes.

Jim