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### Expected time to get all four unique coupons [duplicate]

Envelopes are on sale for Rs. 30 each. Each envelope contains exactly one coupon, which can be one of four types with equal probability. Suppose you keep on buying envelopes and stop when you collect ...
96 views

### Probability of observing all cards? [duplicate]

I have a stack of $n$ distinct cards. I randomly draw $N$ cards from the stack with replacement. Assume that $N \ge n$. What is the probability that I observe all cards at least once? I got this far:...
56 views

### Probability Problem [duplicate]

I have a question about a probability problem located here: http://www.statisticshowto.com/probability-and-statistics/probability-main-index/ And quoted here: “If you were trying to collect 6 ...
46 views

### How many random to get n unique integers [duplicate]

How many random integers from (1-n) must I produce to get all n integers Assume a perfect random Because of duplicates it will be more than n I understand there will be variance but is there an ...
33 views

### Expected value question [duplicate]

Say I am rolling a 20-sided die. What is the expected number of rolls to have rolled each number? I haven't taken statistics in a while so my syntax might be off but this question has been bugging me ...
23k views

### Generic sum of Gamma random variables

I have read that the sum of Gamma random variables with the same scale parameter is another Gamma random variable. I've also seen the paper by Moschopoulos describing a method for the summation of a ...
4k views

### What are the chances rolling 6, 6-sided dice that there will be a 6?

More generally, what is the probability that n n-sided dice will turn up at least one side with the highest number ("n")? My crude thinking is that each side has 1/6 probability, so that 6 ...
849 views

### Expected number of times to roll a die until each side has appeared 3 times

What is the expected number of times you must roll a die until each side has appeared 3 times? This question was asked in primary school in New Zealand and it was solved using simulations. What is ...