I won't answer your question because no one can, and in any case I
prefer not to respond to people who hide behind handles.
This is a good example of what I call an over formulated problem.
Individual A has a problem which he thinks individual E can solve, so
instead of simply stating the problem, A reformulates it in terms which
A believes to belong to the domain of expertise of E. This distorts the
problem. Sometimes the distorted problem makes a sort of sense, and E
will attempt an answer. If there are several E's, they may interpret the
problem variously, and respond variously.
In this particular case, I suspect the poster is not very familiar with
measures of variability, and consequently mis-thinks that the answer to
the problem behind the post lies in something called "expected income
variance," whatever that may be. I can only guess at what the problem
behind the question might be.
Eddy wrote:
> Suppose A's income is 100 in the year 1, and his income is expected
> to be anywhere between 110 and 120 in the year 2. What would be a
> reasonable estimate of A's (expected) income variance from year 1 to
> year 2? (Hey, not a homework question.)
>
> At first, I thought I would calculate the variance from the pair of
> numbers {100, 115} and take it as the income variance. (115 is the
> median of 110 and 120, and I take it as a "reasonable" approximation
> of the second year income.) However, I don't feel quite right about
> this.
>
> I am now thinking of taking the variances from the pairs {100, 120}
> and {100, 110}, and then use the difference of the variances as my
> answer to the question. Intuitively, the variance of {100, 110}
> provides the lower bonds of A's income variance, and that of {100,
> 120} is the upper bound. However, I am still very doubtful.
>
> Any suggestion of how to give a reasonable estimate of the income
> variance in the above case? (Assuming uniform distribution between
> 110 and 120 is acceptable, if this assumption would help.) Thanks in
> advance.
--
Bob Wheeler --- http://www.bobwheeler.com/
ECHIP, Inc. ---
Randomness comes in bunches.
.
.
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