HW5 2.2

[Xiaolong Shen]

Hi,

I'm a little confused about the annotation \pi(x_i). If \pi(i)=j means x_j is the parent of x_i as stated, what does \pi(x_i) mean?

Best

Xiaolong

[Yitong Zhou]

Second that, should I consider that x_i can decide \pi(x_i), which means H[\pi(x_i)|x_i] should be 0 since as long as x_i is fixed, there is only one possible parent choice?

[Sam Zhang]

I think that x_i is an event with multiple choices so is \pi(x_i).

Hence, given x_i, we know x_j = \pi(x_i), the parent event, but not the outcome of that event.

Hence,  H[\pi(x_i)|x_i] is not 0.

Sam