I need to compare microarray data, where all of the "cases" were hybridized in one batch and all of the "controls" in another, so I have no way of removing this batch effect. What would be the best ...
Possible Duplicate: Correlation does not mean causation What is your favorite example of a confounding variable / confounding effect?
Imagine that you are planning a study about risk behaviours among HIV positive injecting drug users. All the individuals included in the sample are injecting drugs and all are HIV positive. The main ...