Re: Probablity questions

Thanks Mr/Ms. Vickson for your help.

2) Let a = posiitive real number. A random variable X with PMF
Px(x)=(a^x)/(1+a)^x+1.Is the denominator equal to 1 + (1+a)^x or to (1+a)^(x+1)? I would
guess the former, but your notation is a bit ambiguous. Also: the
terminology PMF is usually reserved for discrete random variables
(taking at most countably many distinct values), while probability
DENSITY function is used for continuous r.v's. Which type do you
actually mean?

I'm sorry, I should have labelled this as "probability-discrete random
probability". I'm quite new to this subject still and did not realize
the scope of meaning of "PMF." Learn something new everyday, eh?


Compute the expection of X.
Now I know how to figure the expection of a die (unfair or no) but how
do you untangle an equation like above to something of that form?What does this sentence mean? What is there to "untangle"? Again, how
far have you gotten already, and where are you stuck?

As to what I mean by "untangle", the examples I have seen in computing
the expection of a fair die is simply put as the sum of x*p(x). In
this instance, I first tried to substitute x with real values where
x = 0,1,2,3 (to start), is this what I need to do? Just formulate an
equation once I substitute?

The equation really should be.
Px(x)=(a^x)/((1+a)^(x+1)), sorry, that was my mistake.


4. By "solve", do you mean the original problem of finding the k
giving
ratio < 1/3, or do you mean the problem of assigning meaning to the
ratio?

yes. sorry to say I did the obvious, I put in numbers that would make
that ratio correct then will work backwards using the formula to solve
for k.

Thank you for your help, seriously, I have a few things to try on these
word problems now instead of staring blankly at them or webbing thru
hundreds (ok so I exaggerated. not hundreds but lots of em) of pages
trying to find information that could shed light on these problems in
specific.

Thanks again,
Taria

.

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