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Discrete Random Variables: Homework is part of the collection col10555 written by Barbara Illowsky and Susan Dean Homework and provides a number of homework exercises related to Discrete Random Variables (binomial, geometric, hypergeometric and Poisson) with contributions from Roberta Bloom.

1. Complete the PDF and answer the questions.

x size 12{x} {} P ( X = x ) size 12{P \( X=x \) } {} x P ( X = x ) size 12{x cdot P \( X=x \) } {}
0 0.3
1 0.2
2
3 0.4

  • Find the probability that x = 2 size 12{X=2} {} .
  • Find the expected value.

  • 0.1
  • 1.6

Suppose that you are offered the following “deal.” You roll a die. If you roll a 6, you win $10. If you roll a 4 or 5, you win $5. If you roll a 1, 2, or 3, you pay $6.

  • What are you ultimately interested in here (the value of the roll or the money you win)?
  • In words, define the Random Variable X size 12{X} {} .
  • List the values that X size 12{X} {} may take on.
  • Construct a PDF.
  • Over the long run of playing this game, what are your expected average winnings per game?
  • Based on numerical values, should you take the deal? Explain your decision in complete sentences.

A venture capitalist, willing to invest $1,000,000, has three investments to choose from. The first investment, a software company, has a 10% chance of returning $5,000,000 profit, a 30% chance of returning $1,000,000 profit, and a 60% chance of losing the million dollars. The second company, a hardware company, has a 20% chance of returning $3,000,000 profit, a 40% chance of returning $1,000,000 profit, and a 40% chance of losing the million dollars. The third company, a biotech firm, has a 10% chance of returning $6,000,000 profit, a 70% of no profit or loss, and a 20% chance of losing the million dollars.

  • Construct a PDF for each investment.
  • Find the expected value for each investment.
  • Which is the safest investment? Why do you think so?
  • Which is the riskiest investment? Why do you think so?
  • Which investment has the highest expected return, on average?
  • $200,000;$600,000;$400,000
  • third investment
  • first investment
  • second investment

A theater group holds a fund-raiser. It sells 100 raffle tickets for $5 apiece. Suppose you purchase 4 tickets. The prize is 2 passes to a Broadway show, worth a total of $150.

  • What are you interested in here?
  • In words, define the Random Variable X size 12{X} {} .
  • List the values that X size 12{X} {} may take on.
  • Construct a PDF.
  • If this fund-raiser is repeated often and you always purchase 4 tickets, what would be your expected average winnings per raffle?

Suppose that 20,000 married adults in the United States were randomly surveyed as to the number of children they have. The results are compiled and are used as theoretical probabilities. Let X size 12{X} {} = the number of children

x size 12{x} {} P ( X = x ) size 12{P \( X=x \) } {} x P ( X = x ) size 12{x cdot P \( X=x \) } {}
0 0.10
1 0.20
2 0.30
3
4 0.10
5 0.05
6 (or more) 0.05

  • Find the probability that a married adult has 3 children.
  • In words, what does the expected value in this example represent?
  • Find the expected value.
  • Is it more likely that a married adult will have 2 – 3 children or 4 – 6 children? How do you know?
  • 0.2
  • 2.35
  • 2-3 children

Suppose that the PDF for the number of years it takes to earn a Bachelor of Science (B.S.) degree is given below.

x size 12{x} {} P ( X = x ) size 12{P \( X=x \) } {}
3 0.05
4 0.40
5 0.30
6 0.15
7 0.10

  • In words, define the Random Variable X size 12{X} {} .
  • What does it mean that the values 0, 1, and 2 are not included for x size 12{X} {} in the PDF?
  • On average, how many years do you expect it to take for an individual to earn a B.S.?

Questions & Answers

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Odigie Reply
evolutionary history and relationship of an organism or group of organisms
AI-Robot
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Deng
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Hajah Reply
the study of living organisms and their interactions with one another and their environments
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HOW CAN MAN ORGAN FUNCTION
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the diagram of the digestive system
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Ogenrwot
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William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
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Josephine Reply
Genetics is the study of heredity
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Joseph Reply
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the study of living organisms and their interactions with one another and their environment.
Wine
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Joseph Reply
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Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
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cells is the basic structure and functions of all living things
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ISCONT Reply
is organisms that are similar into groups called tara
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Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
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Source:  OpenStax, Collaborative statistics (custom lecture version modified by t. short). OpenStax CNX. Jul 15, 2013 Download for free at http://cnx.org/content/col11543/1.1
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