<Tr> <Td> </Td> <Td> 0 </Td> <Td> </Td> <Td> 0 </Td> <Td> </Td> <Td> 0 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> 0 </Td> <Td> </Td> <Td> </Td> <Td> 0 </Td> <Td> </Td> <Td> 0 </Td> </Tr> <P> Then the unconditional probability that A = 1 is 3 / 6 = 1 / 2 (since there are six possible rolls of the die, of which three are even), whereas the probability that A = 1 conditional on B = 1 is 1 / 3 (since there are three possible prime number rolls--2, 3, and 5--of which one is even). </P> <P> Similarly for continuous random variables, the conditional probability density function of Y given the occurrence of the value x of X can be written as </P>

If the conditional distributions of y change the variables are