Statistics 3

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Curso Estatística 
Teste Atividade - Statistics 3 
Iniciado 17/07/20 00:39 
Enviado 17/07/20 01:29 
Status Completada 
Resultado da 
tentativa 
9 em 10 pontos 
Tempo decorrido 49 minutos 
Resultados exibidos Respostas enviadas, Respostas corretas, 
Comentários 
 Pergunta 1 
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. 
 
Of the individuals who did not contract Disease 2, what proportion will 
not contract Disease 1? 
 
Resposta Selecionada: 
.78/.85 
Resposta Correta: 
.78/.85 
Feedback da 
resposta: 
This is correct. P(Not B | Not A)=P(Not A and Not 
B)/P(Not A)=.78/.85 
 
 
 Pergunta 2 
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. 
 
A random sample of 21 credit card users is chosen.What is the mean 
and standard deviation of pˆ, the sample proportion of credit card users 
who pay their bill in full every month? (some answers are rounded). 
Resposta Selecionada: 
Mean = 0.30, standard deviation = 0.1 
Resposta Correta: 
Mean = 0.30, standard deviation = 0.1 
Feedback 
da 
resposta: 
This is correct. The mean is the population proportion p 
= 0.30 and the standard deviation is 
p(1−p)n−−−−−√=.3(1−.3)21−−−−−−√=0.1 
 
 
 Pergunta 3 
1 em 1 pontos 
 
This is correct. Since the events “belongs to Middle Class” and “belongs 
to Upper Class” are disjoint, P(Middle 
or Upper)=P(Middle)+P(Upper)=.50+.21=.71 
 
 
 
Apply probability rules in order to find the likelihood of an event 
"Fill in the blank" question: select the correct answer. 
Two U.S. adults are chosen at random.Let A be the event that the first 
adult belongs to the Middle ClassLet B be the event that the second 
adult belongs to the Lower class. 
Complete the following sentences: 
Events A and B are 
.Events A and B are 
 
 
Resposta Selecionada: 
Disjoint 
Resposta Correta: 
Disjoint 
Feedback da resposta: This is correct. 
 
 
 Pergunta 4 
1 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: 
 
Both np = 1600 * 0.1 = 160 ≥ 10 and n(1 - p) = 
1600 * 0.9 = 1440 ≥ 10 
Resposta Correta: 
Both np = 1600 * 0.1 = 160 ≥ 10 and n(1 - p) = 
1600 * 0.9 = 1440 ≥ 10 
Feedback da resposta: This is correct. 
 
 
 Pergunta 5 
1 em 1 pontos 
 
This is correct. This is the only incorrect statement. 
A 2015 CNN Money article provided the following information about the 
social class distribution of U.S. adults. 
 
 
 
Apply probability rules in order to find the likelihood of an event 
"multiple choice" question: select the correct answer. 
Two U.S. adults are chosen at random. 
Which of the following is the probability that first chosen is Middle Class 
and the second chosen is Lower Class? In other words, which of the 
 
following is P(A and B), where events A and B are as defined in 
Question #8. 
 
Resposta Selecionada: 
.50 * .29 
Resposta Correta: 
.50 * .29 
Feedback da 
resposta: 
This is correct. P(A and B) = [A, B independent] = 
P(A) * P(B) = .50 * .29 
 
 
 Pergunta 6 
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. Suppose that the 
average number of defects in the sample of n=225cars was found to 
be x̅=5.1. What is the z-score of this average? 
 
 
Resposta Selecionada: 
3 
Resposta Correta: 
3 
Feedback da 
resposta: 
This is correct. Z=x¯ 
−μσn√=5.1−3.67.5225√=1.50.5=3 
 
 
 Pergunta 7 
1 em 1 pontos 
 
A patient with a failing heart is waiting for a heart transplant. If a 
suitable transplant is found, the patient’s chances of survival are much 
higher than the patient’s chances of survival if a suitable transplant is 
not found. 
Let T be the event that a suitable Transplant is found. 
Let S be the event that the patient Survives 
The following probability tree summarizes the patient’s chances of 
finding a suitable transplant and survival. 
 
 
 
Use the tree to answer the following questions: 
Use Probability Trees as a tool to find probabilities 
Use the general multiplication rule to find P(A and B) 
"multiple choice" question: select the correct answer. 
What is the probability that a suitable transplant is found and the 
patient survives? 
 
Resposta Selecionada: 
.225 
Resposta Correta: 
.225 
Feedback da 
resposta: 
This is correct. P(T and 
S)=P(T)*P(S|T)=.30*.75=.225 
 
 
 Pergunta 8 
0 em 1 pontos 
 
A family eats out twice a month – once during the first week of the 
month and once during the third week of the month, in one of the three 
 
local restaurants: R1, R2, or R3. Thus the outcome (R3, R2) denotes 
that on a given month the family eats in R3 during the first week of the 
month and in R2 during the third week of the month. It is possible for 
the family to eat at the same restaurant both on the first week and on 
the third week of the month. 
Determine the sample space of a random experiment and identify 
which outcomes are included in a particular event 
"multiple choice" question: select the correct answer. 
Let A be the event that on a given month the family eats in R2 exactly 
once. What are the possible outcomes for this event? 
 
Resposta 
Selecionada: 
 
{ (R2, R2) (R1, R2) (R2, R1) (R2, R3) (R3, 
R2) } 
Resposta Correta: 
{ (R1, R2) (R2, R1) (R2, R3) (R3, R2) } 
 
 
 Pergunta 9 
1 em 1 pontos 
 
A large cable company provides the following information regarding its 
customers: 
· 50% of all customers subscribe to internet service. 
· If a customer is an internet subscriber, there is 64% chance that 
he/she is also a phone subscriber. 
· If a customer is a phone subscriber, there is 80% chance that he/she 
is also an internet subscriber. 
Let A be the event that a customer subscribes to internet service 
Let B be the event that a customer subscribes to phone service 
Determine whether two events are independent 
"multiple choice" question: select the correct answer. 
Are the two subscriptions (phone, Internet) independent of each other? 
 
 
Resposta 
Selecionada: 
 
No, since P(A)=.50 is not equal to P(A|B) = 
.80 
Resposta Correta: 
No, since P(A)=.50 is not equal to P(A|B) = 
.80 
Feedback da resposta: This is correct. 
 
 Pergunta 10 
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. 
 
 
Sexta-feira, 31 de Julho de 2020 21h14min55s BRT 
 
	 Pergunta 1
	 Pergunta 2
	 Pergunta 3
	 Pergunta 4
	 Pergunta 5
	 Pergunta 6
	 Pergunta 7
	 Pergunta8
	 Pergunta 9
	 Pergunta 10