Chapter 7: Problem 6
A fair die is rolled 10 times. Calculate the expected sum of the 10 rolls.
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Chapter 7: Problem 6
A fair die is rolled 10 times. Calculate the expected sum of the 10 rolls.
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A prisoner is trapped in a cell containing 3 doors. The first door leads to a tunnel that returns him to his cell after 2 days' travel. The second leads to a tunnel that returns him to his cell after 4 days' travel. The third door leads to freedom after 1 day of travel. If it is assumed that the prisoner will always select doors \(1,2,\) and 3 with respective probabilities \(.5,3,\) and \(.2,\) what is the expected number of days until the prisoner reaches freedom?
Cards from an ordinary deck are turned face up one at a time. Compute the expected number of cards that need to be turned face up in order to obtain (a) 2 aces; (b) 5 spades; (c) all 13 hearts.
A certain region is inhabited by \(r\) distinct types of a certain species of insect. Each insect caught will, independently of the types of the previous catches, be of type \(i\) with probability $$ P_{i}, i=1, \ldots, r \quad \sum_{1}^{r} P_{i}=1 $$ (a) Compute the mean number of insects that are caught before the first type 1 catch. (b) Compute the mean number of types of insects that are caught before the first type 1 catch.
If 101 items are distributed among 10 boxes, then at least one of the boxes must contain more than 10 items. Use the probabilistic method to prove this result.
A population is made up of \(r\) disjoint subgroups. Let \(p_{i}\) denote the proportion of the population that is in subgroup \(i, i=1, \ldots, r .\) If the average weight of the members of subgroup \(i\) is \(w_{i}, i=1, \ldots, r\) what is the average weight of the members of the population?
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