Chapter 4: Q.4.6 (page 163)
In Problem for if the coin is assumed fair, what are the probabilities associated with the values that X can take on?
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Chapter 4: Q.4.6 (page 163)
In Problem for if the coin is assumed fair, what are the probabilities associated with the values that X can take on?
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Find Var(X) and Var(Y) for X and Y as given in Problem 4.21
The number of times that a person contracts a cold in a given year is a Poisson random variable with parameter . Suppose that a new wonder drug (based on large quantities of vitamin ) has just been marketed that reduces the Poisson parameter to for percent of the population. For the other percent of the population, the drug has no appreciable effect on colds. If an individual tries the drug for a year and has colds in that time, how likely is it that the drug is beneficial for him or her?
Each of 500 soldiers in an army company independently has a certain disease with probability 1/103. This disease will show up in a blood test, and to facilitate matters, blood samples from all 500 soldiers are pooled and tested.
(a) What is the (approximate) probability that the blood test will be positive (that is, at least one person has the disease)? Suppose now that the blood test yields a positive result.
(b) What is the probability, under this circumstance, that more than one person has the disease? Now, suppose one of the 500 people is Jones, who knows that he has the disease.
(c) What does Jones think is the probability that more than one person has the disease? Because the pooled test was positive, the authorities have decided to test each individual separately. The first i − 1 of these tests were negative, and the ith one—which was on Jones—was positive.
(d) Given the preceding scenario, what is the probability, as a function of i, that any of the remaining people have the disease?
A man claims to have extrasensory perception. As a test, a fair coin is flipped times and the man is asked to predict the outcome in advance. He gets out of correct. What is the probability that he would have done at least this well if he did not have ESP?
Here is another way to obtain a set of recursive equations for determining , the probability that there is a string of consecutive heads in a sequence of flips of a fair coin that comes up heads with probability :
(a) Argue that for , there will be a string of consecutive heads if either
1. there is a string of consecutive heads within the first flips, or
2. there is no string of consecutive heads within the first flips, flip is a tail, and flips are all heads.
(b) Using the preceding, relate . Starting with , the recursion can be used to obtain , then, and so on, up to .
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