Friday, January 25, 2019

probability - 6 sided die probabilities

i am currently working on a study guide and one of the questions i am completely stuck on and have no idea how to do it. Question is. You are interested in the number of rolls of a fair $6$ sided die until a number $2$ shows up.


Let $X =$ The number of times you roll the die until a number $2$ shows up.


(a) What type of random variable is $X$?


(b) How many rolls do you expect it to take? That is, what is the expected value, or mean, of the random variable $X$?


(c) What is the probability you roll a $2$ for the first time on the fourth roll? i.e. What is $P(X = 4)$?

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