Avaliação - Statistics 3 - Probabilitypt

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Pergunta 1 
0 em 1 pontos 
 The weekly cost of maintenance and repairs for a company has a normal distribution 
with mean μ=$5500 and standard deviation σ=$400. 
Note: For questions 19 and 20 you will need to use the Normal Table linked here 
Use the normal distribution as an approximation to the binomial distribution 
"multiple choice" question: select the correct answer. 
Which of the following is the correct justification for reliably using the normal 
approximation for X? 
 
 
Resposta 
Selecionada: 
 
n = 1600 ≥ 30 
Resposta Correta: 
Both np = 1600 * 0.1 = 160 ≥ 10 and n(1 - p) = 1600 * 0.9 
= 1440 ≥ 10 
 
 
Pergunta 2 
0 em 1 pontos 
 
The following three probability histograms represent the probability distributions of 
the random variables X, Y, and W. 
As is evident from the probability histograms, the mean of all three random variables 
is 5. 
Find the mean and variance of a discrete random variable, and apply these 
concepts for solving real world problems. 
"multiple choice" question: select the correct answer. 
Which of the three random variables has the largest standard deviation? 
 
 
Resposta Correta: 
X 
 
 
Pergunta 3 
1 em 1 pontos 
 
 
An epidemiological study investigated the prevalence of two contagious 
diseases ( Disease 1 and Disease 2) in the U.S. 
Let A be the event that an individual contracts Disease 1 
Let B be the event that an individual contracts Disease 2 
Understand the reasoning behind the concept of conditional probability, 
calculate conditional probabilities and interpret them. 
"multiple choice" question: select the correct answer. 
What is the interpretation of P(B|A) in the context of this study? 
 
 
 
Resposta Selecionada: 
(D) and (E) are both interpretations of P(B|A). 
Resposta Correta: 
(D) and (E) are both interpretations of P(B|A). 
Feedback da resposta: This is correct. 
 
 
Pergunta 4 
1 em 1 pontos 
 
Understand how probability quantifies uncertainty and relate the probability of 
an event to the likelihood of the event occurring. 
"multiple choice" question: select the correct answer. 
Which of the following is true regarding a probability of an event P(A)? 
 
 
Resposta Selecionada: 
0≤P(A)≤1 
Resposta Correta: 
0≤P(A)≤1 
 
Feedback da 
resposta: 
This is correct. The probability of an event can any number 
between 0 and 1, including 0 and 1. In other words, the 
probability of an event cannot be more than 1 or less than 0. 
 
Pergunta 5 
0 em 1 pontos 
 
An epidemiological study investigated the prevalence of two contagious 
diseases ( Disease 1 and Disease 2) in the U.S. 
Let A be the event that an individual contracts Disease 1 
Let B be the event that an individual contracts Disease 2 
Understand the reasoning behind the concept of conditional probability, 
calculate conditional probabilities and interpret them. 
"multiple choice" question: select the correct answer. 
 
Of the individuals who did not contract Disease 2, what proportion will not 
contract Disease 1? 
 
Resposta Selecionada: 
.78 
Resposta Correta: 
.78/.85 
 
 
Pergunta 6 
0 em 1 pontos 
 
Skill: Determine the sampling distribution of the sample proportion and the sample 
mean in a given situation and apply it to determine likelihoods. 
"multiple choice" question: select the correct answer. 
20% of all the students at a large university are international students. Two random 
samples of students are chosen; a random sample of n=64 students and a random 
sample of n=400 students. In which of the two samples is it more likely that more 
than 25% of the sampled students are international students? 
 
Resposta 
Selecionada: 
 
The sample of size n=400 since in there is more variability in the 
proportion of international students in larger samples. 
 
Resposta 
Correta: 
 
The sample of size n=64 since in there is more variability in the 
proportion of international students in smaller samples. 
 
Pergunta 7 
1 em 1 pontos 
 
An epidemiological study reported the following information about two contagious 
diseases: 
· There is 15% chance of contracting Disease I 
· There is 20% chance of contracting Disease II 
· There is 2% chance of contracting both diseases 
Let A be the event that a randomly chosen person contracts Disease I 
Let B be the event that a randomly chosen person contracts Disease II 
Apply probability rules in order to find the likelihood of an event 
"multiple choice" question: select the correct answer. 
What does the probability P(A or B) mean in this context? 
 
 
Resposta 
Selecionada: 
 
The probability of contracting at least one of the two 
diseases 
Resposta Correta: 
The probability of contracting at least one of the two 
diseases 
Feedback da 
resposta: 
This is correct. P(A or B) is the probability of contracting 
Disease I or Disease II or both. In other words, P(A or B) is the 
probability of contracting at lease one of the two diseases. 
 
 
Pergunta 8 
1 em 1 pontos 
 
Understand how probability quantifies uncertainty and relate the probability of 
an event to the likelihood of the event occurring. 
"multiple choice" question: select the correct answer. 
 
Let A be the event that a document will reach its destination on time using a 
certain service. If P(A)=.98 
this means that: 
 
Resposta 
Selecionada: 
 
The document will almost always reach its destination on 
time 
Resposta Correta: 
The document will almost always reach its destination on 
time 
Feedback da resposta: This is correct. 
 
 
Pergunta 9 
1 em 1 pontos 
 
Skill: Determine the sampling distribution of the sample proportion and the sample 
mean in a given situation and apply it to determine likelihoods. 
"multiple choice" question: select the correct answer. 
Is it safe to assume that the sampling distribution of pˆ is approximately normal for 
random samples of size n=21? 
 
Resposta Selecionada: 
No, since n*p is not greater than 10. 
Resposta Correta: 
No, since n*p is not greater than 10. 
Feedback da resposta: This is correct. 
 
 
• Pergunta 10 
0 em 1 pontos 
 
The probability table below summarizes the information that a large cable company 
provides about its customers: 
 
Where: 
T is the event that a randomly chosen customer subscribes to TV service 
I is the event that a randomly chosen customer subscribes to Internet service 
 
 
 
Create a probability table to organize and summarize information and use it to 
find probabilities 
"multiple choice" question: select the correct answer. 
What is the correct representation and probability of the event that a customer 
subscribes only to TV service? 
 
Resposta Selecionada: 
P(Not I) = .05 
Resposta Correta: 
P(T and Not I) = .05