# Evaluation of a probability using Markov's inequality

#### Mishe Mitasek

##### New Member
X,Y and Z are independent RVs with a MGF Mx(t)=1/(1−t).
How can I evaluate in the most efficient manner P(X+Y+Z>6)?

Thank you

#### Dason

Do you know what distribution that mgf belongs to? That's step one. The sum of three independent rvs with that distribution also make a known distribution.

#### Dason

Actually... Were you told to use markovs inequality? Because I guess you wouldn't explicitly need to figure out what distribution that is for if that's the case.

#### katxt

##### Active Member
Do you know what distribution that mgf belongs to?
Exponential with rate 1, perhaps? So something to do with gamma. It's been so long....

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#### katxt

##### Active Member
In Excel type =1-GAMMADIST(6,3,1,1) ( I think... You're unlikely to get more efficient than that if it's true.)

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