Chapter 4: Q. 39 (page 285)
What values does the random variable X take on?
The values are
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Use the following information to answer the next six exercises: The Higher Education Research Institute at UCLA collected data from 203,967 incoming first-time, full-time freshmen from 270 four-year colleges and universities in the U.S. 71.3% of those students replied that, yes, they believe that same-sex couples should have the right to legal marital status. Suppose that you randomly select freshman from the study until you find one who replies โyes.โ You are interested in the number of freshmen you must ask.
On average (ฮผ), how many freshmen would you expect to have to ask until you found one who replies "yes?"
The World Bank records the prevalence of HIV in countries around the world. According to their data, โPrevalence of HIV refers to the percentage of people ages 15 to 49 who are infected with HIV.โ[1] In South Africa, the prevalence of HIV is 17.3%. Let X = the number of people you test until you find a person infected with HIV.
a. Sketch a graph of the distribution of the discrete random variable X.
b. What is the probability that you must test 30 people to find one with HIV?
c. What is the probability that you must ask ten people?
d. Find the
(i) mean and
(ii) standard deviation of the distribution of X.
What is the probability the baker will sell more than one batch?
Use the following information to answer the next five exercises: Suppose that a group of statistics students is divided into two groups: business majors and non-business majors. There are business majors in the group and seven non-business majors in the group. A random sample of nine students is taken. We are interested in the number of business majors in the sample.
In words, define the random variable .
Use the following information to answer the next five exercises: Suppose that a group of statistics students is divided into two groups: business majors and non-business majors. There are business majors in the group and seven non-business majors in the group. A random sample of nine students is taken. We are interested in the number of business majors in the sample.
What values does take on?
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