# Tagged Questions

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### Confusion related to expectation notation

I have a confusion regarding notation of the expectation. Consider the following: $$E_x(x^2) = \sum_x x^2p(x)$$ $$E_x(x|y) = \sum_x xp(x|y)$$ So the same notation here is giving different meaning ...
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### Probability notation question [duplicate]

I am reading the Hidden Markov Model note http://cs229.stanford.edu/section/cs229-hmm.pdf from Stanford and have problem finding the meaning of the notation described below. What does the semicolon ...
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### Denotation of probability symbols

May I kindly clarify if the following mean the same thing? $$P(AB) = P(A \cap B)$$ Cheers.
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### Why are probability distributions denoted with a tilde?

What is the meaning of the tilde when specifying probability distributions? For example: $$Z \sim \mbox{Normal}(0,1).$$
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### What is the meaning of the semicolon in $f(x;\Theta)$? [duplicate]

In section 6.2, in the second paragraph of p. 335 (image below) of "Probability and statistical inference 7e" by Hogg and Tanis states: perhaps it is known that ...
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### When should I use $E(X)$ and when to use $\mu$ for the mean?

I see that $E(X)$ and $\mu_x$ are used to refer to the mean of some distribution or variate, but I am not clear on what circumstances each is appropriate. $E(X)$ seems to always be more often in the ...
### Meaning of probability notations $P(z;d,w)$ and $P(z|d,w)$
What is the meaning between the notation $P(z;d,w)$ and $P(z|d,w)$ which is commonly used in many books and papers?
### What does $d$ mean in this notation of the “usual noninformative prior of $\mu_i$ and $\sigma_i$?”
Samiuddin, (1976) states: or, typset with $\LaTeX$ as originally posted We start with the usual noninformative prior distribution of $\mu_i$ and $\sigma_i (i = 1,2,\ldots, k)$ ...