in 1990 there were about 5.4 billion people in the world. if the population has been growing at 1.95% per year, estimate the yea
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The expected length of code for one encoded symbol is
where is the probability of picking the letter
, and
is the length of code needed to encode
.
is given to us, and we have
so that we expect a contribution of
bits to the code per encoded letter. For a string of length , we would then expect
.
By definition of variance, we have
For a string consisting of one letter, we have
so that the variance for the length such a string is
"squared" bits per encoded letter. For a string of length , we would get
.