variable as a whole and this is definition use sum over all possible values the random variable can take on and you take a weighted sum of the probability of take on that value and then log 2 of 1 over P exile ok so this might seem look a little coming out of water but maybe let's get a little bit of intuition for this of why this might be a meaningful way of how you measure entropy which is the amount of uncertainty you have in a distribution and hence there's a lot of uncertainty about the random variable you need more bits to send the cross we