Basic Help with Multiple Regression Results

#1
Can you help?

I'm trying to run a basic multiple regression in SPSS 18.

I have a series of measurements made in cm, and I want to find the effect of four covariants on theses measures. Age, Gender, Ethnicity and Body Surface Area (BSA)

I have entered all of this into the model with dummy variables set up for ethnicity (there are four sub sets of this).

I now know that BSA effects each of the five measurements. Gender effects a couple, Ethnicity effects four of them and age only one.

I have created an equation for each of the five measurements based on the model provided.

My question is this...What do I do now? I have this model to predict the outcome measurements of future events, but how do I relate this back to my raw data, knowing that each of the four covariants (ethnicity, gender age and BSA) are affecting the raw data in some way? Or are they - is this why I don't get it?

Can I carry on and do basics like mean and 95% CI with the raw data?

Can I do T-Tests between different groups (e.g. ethnic vs BSA) using the raw data? And if this is the case, then what use is the equation other than to predict future values?

Any help explaining what I'm sure is actually very simple would be very gratefully received!