Hi all,

Quick summary:
(How) can I perform multiple regression analysis with a very strongly positively 
skewed variable, ideally using SPSS?

I have a dataset comprised of 206 participants been recruited on the basis 
that, where faced with a choice between Option A or Option B only, they 
almost always choose Option A not B. The study aims to predict why they 
might (occasionally) choose Option B not A. The outcome variable is the % of 
times over a 2-week period that Option B not A was chosen (i.e. % = number 
of option B choices / number of choice opportunities).

Frequencies indicate that 87% of participants chose Option A on 100% of 
occasions. 5% of participants chose Option B not A on 10% of occasions. Only 
1% chose Option B not A on the majority of occasions.

I have a number of potential predictor/explanatory variables that I would like 
to test as predictors of participants’ deviation from using Option A all of the 
time. Can such an analysis be meaningfully conducted (using SPSS) with such 
heavy positive skew? If so, how?

(NB - using base 10 logarithm doesn’t work - the skewness Z score, which I 
understand should be less than 1.96, is 35.21, and the base 10 log reduces it 
only to 14.55.)

Ben Gardner