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Ch. 4 - Probability
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 4, Problem 4.4.28c

Phase I of a Clinical Trial A clinical test on humans of a new drug is normally done in three phases. Phase I is conducted with a relatively small number of healthy volunteers. For example, a phase I test of bexarotene involved only 14 subjects. Assume that we want to treat 14 healthy humans with this new drug and we have 16 suitable volunteers available.


c. If 14 subjects are randomly selected and treated at the same time, what is the probability of selecting the 14 youngest subjects?

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1
Step 1: Recognize that this is a probability problem involving combinations. The goal is to calculate the probability of selecting a specific group (the 14 youngest subjects) out of a total of 16 volunteers.
Step 2: Recall the formula for combinations, which is used to determine the number of ways to choose a subset of items from a larger set. The formula is: C=n!r!(n-r)!, where n is the total number of items, r is the number of items to choose, and '!' denotes factorial.
Step 3: Calculate the total number of ways to select 14 subjects from the 16 volunteers. This is given by the combination formula: C(16,14). Substitute n = 16 and r = 14 into the formula.
Step 4: Recognize that there is only one way to select the 14 youngest subjects specifically, as this is a unique group. Therefore, the number of favorable outcomes is 1.
Step 5: Calculate the probability by dividing the number of favorable outcomes (1) by the total number of possible outcomes (the result from Step 3). The probability is given by: 1C(16,14).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Probability

Probability is a measure of the likelihood that a particular event will occur, expressed as a number between 0 and 1. In this context, it refers to the chance of randomly selecting a specific group of subjects from a larger pool. Understanding how to calculate probabilities is essential for determining the likelihood of selecting the 14 youngest subjects from the 16 available volunteers.
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Introduction to Probability

Combinatorics

Combinatorics is a branch of mathematics dealing with combinations and permutations of objects. It is crucial for calculating the number of ways to choose a subset of subjects from a larger group. In this scenario, combinatorial methods will help determine how many different ways the 14 youngest subjects can be selected from the 16 volunteers, which is necessary for calculating the probability.

Random Sampling

Random sampling is a technique used to select a subset of individuals from a larger population in such a way that each individual has an equal chance of being chosen. This concept is important in clinical trials to ensure that the sample is representative and that the results are unbiased. In this question, understanding random sampling is key to determining the probability of selecting the youngest subjects without any bias.
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Sampling Distribution of Sample Proportion
Related Practice
Textbook Question

Surge Protectors Refer to the accompanying figure showing surge protectors p and q used to protect an expensive television. If there is a surge in the voltage, the surge protector reduces it to a safe level. Assume that each surge protector has a 0.985 probability of working correctly when a voltage surge occurs.


c. Which arrangement should be used for better protection?

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Textbook Question

Florida Pick 3 In the Florida Pick 3 lottery, you can place a “straight” bet of \(1 by selecting the exact order of three digits between 0 and 9 inclusive (with repetition allowed), so the probability of winning is 1/1000. If the same three numbers are drawn in the same order, you collect \)500, so your net profit is \$499.


c. Is there much of a difference between the actual odds against winning and the payoff odds?

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Textbook Question

Mega Millions As of this writing, the Mega Millions lottery is run in 44 states. Winning the jackpot requires that you select the correct five different numbers from 1 to 70 and, in a separate drawing, you must also select the correct single number from 1 to 25.


c. How does the probability compare to the probability for the old Mega Millions game which involved the selection of five different numbers between 1 and 75 and a separate single number between 1 and 15?

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Textbook Question

Sampling Eye Color Based on a study by Dr. P. Sorita Soni at Indiana University, assume that eye colors in the United States are distributed as follows: 40% brown, 35% blue, 12% green, 7% gray, 6% hazel.


d. If two people are randomly selected, what is the probability that at least one of them has brown eyes?

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Textbook Question

In Exercises 21-28, find the probability and answer the questions.


X-Linked Genetic Disease Men have XY (or YX) chromosomes and women have XX chromosomes. X-linked recessive genetic diseases (such as juvenile retinoschisis) occur when there is a defective X chromosome that occurs without a paired X chromosome that is not defective. In the following, represent a defective X chromosome with lowercase x, so a child with the xY or Yx pair of chromosomes will have the disease and a child with XX or XY or YX or xX or Xx will not have the disease. Each parent contributes one of the chromosomes to the child.


c. If a mother has one defective x chromosome and one good X chromosome and the father has good XY chromosomes, what is the probability that a son will inherit the disease?

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Textbook Question

Organ Donors USA Today provided information about a survey (conducted for Donate Life America) of 5100 adult Internet users. Of the respondents, 2346 said they are willing to donate organs after death. In this survey, 100 adults were surveyed in each state and the District of Columbia, and results were weighted to account for the different state population sizes.


b. Based on the poll results, what is the probability of randomly selecting an adult who is willing to donate organs after death?


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