Imagine I have a simple electrical circuit on main power. This circuit has only one outlet on it, which is connected only to one floor lamp. Imagine further tha

Imagine I have a simple electrical circuit on main power. This circuit has only one outlet on it, which is connected only to one floor lamp. Imagine further that the light is currently on. If I flip the switch off, what is the probability that the light turns off? If the light goes off, what is the probability that I flipped the switch off? Those probabilities are not identical. --- Imagine that I have been administered a standard FDA-approved HIV test. If I am HIV-negative, what is the likelihood that the test comes back positive? (I.e., what is the false positive rate?) If the test comes back positive, what is the likelihood that I am HIV-negative? Those probabilities are not identical. --- Imagine that your client's DNA is tested against DNA found at a murder scene, comparing the short tandem repeats at 13 locations. There is no other evidence linking your client to the crime scene or to the murder. If your client was not at the scene, what is the likelihood of all 13 loci being matches? If all 13 loci are matches, what is the likelihood your client was not at the scene? Those probabilities are not identical.