this in 3-4 sentences When we wish to identify cause-effect relationships and have the means to conduct an experiment rather than an observational study, we do so. Our ability to explore cause-effect relationships is confounded in observational studies, while experiments "deconfound" such relationships. What is "confounding"? What is a "lurking variable"? What three principles are necessary conditions for an experiment that will deconfound the cause-effect relationship? (I.e., what is the name of each principle, and what does it involve?) What two additional features of an experimental study will improve the quality of the inferences we draw? (I.e., what is the name of each additional feature, and what does it involve?)