for example, we have 3 confounding random variables, x1, x2 and x3 with 3 different variances. If we had to treat each variable alone, we would have used odd ratio or relative risk ( depending on what kind of study we are using whether retrospective or prospective) to determine the risk of the disease given the variable. What if we have 3 variables? how can we combine all of them to the get the odd ratio of diagnosing the disease? Do we have to use logistic regression analysis with the logit as a linear combination function of multiple variables? Also what does it have to do with our specific patient who comes with a combination of x1, x2 and x3, do we have to plug those values into the logistic analysis in order to get the probability of having the disease? To complicate the issue ( although it is not neccessarily at this stage), what if we conduct a metaanalysis with different studies are conducted at different places, how would we combine those data into a the result?