Hi, In my data I have three variables - year, month and day that I want to combine into one date variable with the format ddmmyy8. How can I do that? Thanks - Bodil ... View more

Hi everybody, I need some help with fitting a PO model for the first time... I I'm evaluating the effects of different factors on the cleanliness of cows. My response is a scoring of cleanliness on a scale with four levels: Clean=1 - Covered in dirt=4. I have data from 1362 cows clustered in 44 herds. I started out with 16 explanatory variables - and after backward elimination I'm left with 3-4 categorical and one qualitative explanatory variables. I've checked the PO assumption using PROC LOGISTIC - and the assumption did not hold (p<0.001). If I excluded one of my variables it came closer (p=0,482) . I then assessed the ordinality of my response with respect to each explanatory variable by plotting the mean of each explanatory variables stratified by levels of the response variable. As the means did not differ between score 1 and 2 it suggested, that these two levels should be merged. Which I then did - and ran the PROC LOGISTIC again (with the 'suspicious' variable included again). Now the proportional odds assumption was closer to hold - p=0,0302. My question - for now... - are: * Can I continue with the PO model * Does the test of the PO assumption in PROC LOGISTIC hold when I can't take into account the clustering of my data? * And how do I assess model fit using PROC GENMOD (SAS 9.1)? This became a very long story - I hope that some of you can find the time to help me out! Regards Bodil ... View more