# Questions tagged [probability]

For basic questions about probability and for questions about calculating a probability, expected value, variance, standard deviation, or similar quantity. For questions about the theoretical footing of probability (especially using [tag:measure theory]), ask under [tag:probability-theory] instead. For questions about specific probability distributions, use [tag:probability-distributions] instead.

67,666 questions
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### $X_n$ converges in probability but not almost surely

Consider the sequence $\{X_n\}$ given in Davide Giraudo's answer to this question. As is explained in the answer, the lack of a.s. convergence comes from the Borel-Cantelli lemma. Another way of ...
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### Find the pdf , distribution function of $X$ and $E[(X-2)^2]$

I 'll be very grateful if you can help me , here is the question : When a person sends an email, the probability that there is an attachment is 0.5. If there is an attachment then the size of the ...
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### I need help with calculating probability [duplicate]

I need help with this question: Consider a loaded dice such that the probability to obtain an outcome of 1 is 2p/3, the probability of obtaining 2, 3, 4 or 5 is p each, and the probability of ...
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### Escape time probability distribution

I have a system where a random walker is moving on $\mathbb{Z}$. However, at each point in $\mathbb{Z}$, there is a probability $q$ that an escape route exists along which the walker can escape. I ...
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### Probability that of having exactly two boys

If in a family of 3 children, there is at least 1 boy, what is the probability that there are exactly 2 boys among the children? My attempt: I calculated all the possibilities of the family by ...
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### Operational Meaning of Relative Entropy

Is there an operational meaning to understand the non-negativity of relative entropy between two probability distributions? I understand the mathematical argument/proof. But I want to know if there is ...