There are $n$ types of coupons. Each newly obtained coupon is, independently, type $i$ with probability $p_{i}, i=1, \ldots, n$. Find the expected number and the variance of the number of distinct types obtained in a collection of $k$ coupons.
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Step 1: Let X be the random variable representing the number of distinct types obtained in a collection of k coupons. Show more…
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