Question about continuous and discrete moment generating functions.

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SUMMARY

The discussion centers on the moment generating function (mgf) given by (1/2)(1+e^t) and its implications for continuous and discrete distributions. It is established that this mgf corresponds to a Bernoulli distribution with parameter p = 1/2, which is inherently discrete. Therefore, it is concluded that no continuous random variable can possess this mgf, as the characteristic function theorem indicates that a characteristic function uniquely defines a cumulative distribution function (cdf).

PREREQUISITES
  • Understanding of moment generating functions (mgf)
  • Knowledge of Bernoulli distributions and their properties
  • Familiarity with characteristic functions and cumulative distribution functions (cdf)
  • Basic probability theory concepts
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  • Study the relationship between characteristic functions and cumulative distribution functions
  • Explore the implications of the uniqueness of characteristic functions
  • Learn about other distributions that have specific moment generating functions
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Students and professionals in statistics, probability theory, and data science who are interested in understanding the distinctions between continuous and discrete random variables, particularly in the context of moment generating functions.

The1TL
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Homework Statement



is there a continuous real valued variable X with mgf: (1/2)(1+e^t)

Homework Equations





The Attempt at a Solution


I've noticed that this is the mgf of a bernoulli distribution with p =1/2. But since bernoulli is a discrete distribution, does that disprove that there is a continuous variable with that mgf?
 
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The1TL said:

Homework Statement



is there a continuous real valued variable X with mgf: (1/2)(1+e^t)

Homework Equations





The Attempt at a Solution


I've noticed that this is the mgf of a bernoulli distribution with p =1/2. But since bernoulli is a discrete distribution, does that disprove that there is a continuous variable with that mgf?

There is a theorem that two cdfs are the same if and only if their characteristic functions are the same; in other words, a characteristic function can belong to only one cdf. Of course, the mgf is the characteristic function at an imaginary argument, so the result still applies. Just Google "characteristic function" for more details.
 

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