pml-book
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Book 1. 20220808. Section 3.3.4.
That equality does not hold.
Consider the univariate standard normal distribution and N=4. Suppose the sample is {-1, -1, 1, 1}. Then the joint probability density equals N(1 | mean=0, var=1) ^ 4. The probability density for the sample mean (-1 + -1 + 1 + 1) / 4 = 0 is N(0 | mean=0, var=0.25).
Grab a calculator https://www.danielsoper.com/statcalc/calculator.aspx?id=54, we have that N(1 | mean=0, var=1) ^ 4 is about 0.24 ^ 4 and N(0 | mean=0, var=0.25) is about 0.79. Obviously, they differ.
Intuitively, the probability of a sample mean collects the probability of all possible samples having this sample mean value, and should be larger than the probability of any single such sample.
Same issue in section 4.6.4.2.
Also, that N should be an exponent rather than a numerator.
Missing period.
Re 3.65. I meant to write proportional to, not equality. See https://github.com/probml/pml-book/issues/512
All fixed, thanks.