Range & PMF of Y for X ∼ Geometric(1/3)

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In summary, the range of Y is 0 to infinity, and the PMF for Y is 1/3(2/3)^(k-1) for k = 1,2,3... converted from the PMF for X. The values of X that result in Y = 0 are any values of X that are equal to or greater than 5, and the values of X that result in Y = 1 are any values of X that are less than 5.
  • #1
Jonobro
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Homework Statement


Let X∼Geometric(1/3), and let Y=|X−5|. Find the range and PMF of Y.

Homework Equations


Px(k) = p(1-p)^(k-1) for x=1,2,3...

3. My attempt at a solution
I set up the PMF for Px

Px(k) = 1/3(2/3)^(k-1) for k = 1,2,3,...
However I don't know how to convert this to Y
 
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  • #2
Jonobro said:

Homework Statement


Let X∼Geometric(1/3), and let Y=|X−5|. Find the range and PMF of Y.

Homework Equations


Px(k) = p(1-p)^(k-1) for x=1,2,3...

3. My attempt at a solution
I set up the PMF for Px

Px(k) = 1/3(2/3)^(k-1) for k = 1,2,3,...
However I don't know how to convert this to Y

Really? For what values of ##X## do you get ##Y = 0##? Which value (or values) of ##X## give you ##Y = 1##? Etc., etc.
 

What is the range of Y for X ∼ Geometric(1/3)?

The range of Y for X ∼ Geometric(1/3) is all positive integers from 1 to infinity.

How do you calculate the probability mass function (PMF) of Y for X ∼ Geometric(1/3)?

The PMF of Y for X ∼ Geometric(1/3) is calculated using the formula P(Y = k) = (1-p)^k * p, where p is the probability of success (1/3 in this case) and k is the number of trials.

What does a PMF graph look like for X ∼ Geometric(1/3)?

A PMF graph for X ∼ Geometric(1/3) will have a peak at 1 and then gradually decrease as the value of k increases, forming a right-skewed distribution.

What is the expected value of Y for X ∼ Geometric(1/3)?

The expected value of Y for X ∼ Geometric(1/3) is equal to 1/p, so in this case it is 3.

Can the range of Y for X ∼ Geometric(1/3) be negative?

No, the range of Y for X ∼ Geometric(1/3) cannot be negative as it is a discrete probability distribution only defined for positive integers.

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