Before and after comparison troubles

#1
Hi!

I'm having some trouble with my before and after comparison and hope you guys can help me!

I have asked the same group of respondents to answer questions about their wellbeing and their main travel mode before and after the introduction of a toll scheme. I want to be able to see if there is a statistical difference in people's wellbeing after the introduction of the toll scheme for each travel mode. I have one variable that includes 6 different modes of travel for the "before toll scheme questionnaire" and another variable that includes the same 6 different modes of travel for the "after toll scheme questionnaire". For example, 3 = car in both of them. Then I have two wellbeing variables (range from 1-7), one from the "before toll scheme questionnaire" and another from the "after toll scheme questionnaire". My question to you is, how can I see whether there is a statistical difference in wellbeing among car users (a group whose the members change somewhat between the two points of measurement) when comparing data from before and after the toll was introduced.

I've tried different ways to attack the problem but I just can't figure it out.

Thank you in advance!

/Maria
 

hlsmith

Less is more. Stay pure. Stay poor.
#2
What is your sample size? Most likely you will be looking at examining the differences on the same measures before and after. Depending on the normality of these data residuals you may use one sample t-test or wilcoxon signed rank tests. If you want to compare differences across groups you may be looking at t-test or Wilcoxon rank sum tests.
 
#3
Thanks for replying hlsmith!

My sample size is 650. How can I use those tests when the dependent variable (wellbeing) is measured both before and after (can I use both in one analysis?), and when some people changed main travel mode after the toll was introduced (which means I can't use a simple filter)? Also, the sample isn't independent since the same people were measured twice.. It's the combination of these things that is driving me mad ;)