STATISTIC 3 ATIVIDADE

Prévia do material em texto

Pergunta 1
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.
There is 95% chance in a random sample of n=84 card users, the proportion of those who pay their bills in full every month will be:
	
	
	
	
		Resposta Selecionada:
	 
Between .20 and .40
	Resposta Correta:
	 
Between .20 and .40
	Feedback da resposta:
	This is correct. When n=84, the mean and standard deviation of the sampling distribution are: p = .30 and p(1−p)n−−−−−√=.3(1−.3)84−−−−−−√=0.05, respectively.By the standard deviation rule, there is 95% chance that the sample proportion will be within two standard deviations of its mean. In other words, between .30 – 2(.05) = .20 and .30 + 2(.05) = .40.
	
	
	
Pergunta 2
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
"Fill in the blank" question: select the correct answer.
In this case, X can be approximated by a normal distribution with mean μ=
and standard deviation σ=
	
	
	
	
		Resposta Selecionada:
	 
160
	Resposta Correta:
	 
160
	Feedback da resposta:
	This is correct. The mean of the normal approximation is the mean of the binomial distribution which is np=1600*0.1=160.
	
	
	
Pergunta 3
0 em 1 pontos
	
	
	
	Skill: Distinguish between a parameter and a statistic and recognize the concept of sampling variability.
"multiple choice" question: select the correct answer. 
Which of the following statements is consistent with the idea of sampling variability?
	
	
	
	
		Resposta Selecionada:
	 
If we were to select a different random sample of 625 newborns, the mean and standard deviation in this sample will be exactly the same as in the first sample -- 3450 and 490, respectively.
	Resposta Correta:
	 
If we were to select a different random sample of 625 newborns, we can expect the mean and standard deviation in this sample to be different than the mean and the standard deviation in the first sample. 
	
	
	
Pergunta 4
1 em 1 pontos
	
	
	
	Find the mean and variance of a linear transformation of a random variable, and the mean and variance of the sum of two independent random variables.
"multiple choice" question: select the correct answer.
Based on accumulated data, a propane gas company determined that the random variable X, the number of gallon required to fill a customer’s propane tank, has mean μx=300 gallons and standard deviation σx=40 gallons. The company charges the customer $25 service fee plus $2.50 per gallon of propone.
What is the mean and standard deviation of the amount that a customer is billed for?
	
	
	
	
		Resposta Selecionada:
	 
mean = $775, standard deviation = $100
	Resposta Correta:
	 
mean = $775, standard deviation = $100
	Feedback da resposta:
	This is correct.
	
	
	
	
	
Pergunta 5
0 em 1 pontos
	
	
	
	A lot of research is conducted on the sleeping habits of U.S. adults. One study reported that X, the amount of sleep per night of U.S. adults follows a normal distribution with mean μ=7.5 hours and standard deviation σ=1.2 hours.
Understand how a density function is used to find probabilities involving continuous random variables.
"multiple choice" question: select the correct answer.
The shaded area in the image below represents which of the following probabilities?
	
	
	
	
		Resposta Selecionada:
	 
P(X=8.5 or X=9.5)
	Resposta Correta:
	 
P(8.5<X≤9.5)
	
	
	
Pergunta 6
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.
The study reported the following:
· There is 15% chance of contracting Disease 1
· There is 10% chance of contracting Disease 2
· There is 3% chance of contracting both Disease 1 and Disease 2
Which of the following is true regarding P(B|A)?
	
	
	
	
		Resposta Selecionada:
	 
P(B|A) = .015
	Resposta Correta:
	 
P(B|A) = .20
	
	
	
Pergunta 7
1 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:
	 
{ (R1, R2) (R2, R1) (R2, R3) (R3, R2) }
	Resposta Correta:
	 
{ (R1, R2) (R2, R1) (R2, R3) (R3, R2) }
	Feedback da resposta:
	This is correct.
	
	
	
	
	
Pergunta 8
0 em 1 pontos
	
	
	
	Airlines sometimes overbook flights. Suppose that for a plane with 111 seats an airline takes 115 reservations. Let the random variable X be the number of people who actually show up (out of the 115 who bought a ticket). From past experience the probability distribution of X is given in the following table:
x 108 109 110 111 112 113 114 115
P(X=x) 0.14 0.16 0.24 0.20 0.13 0.06 0.05 0.02
Find the probability distribution function of a discrete random variable and use it to find probabilities
"multiple choice" question: select the correct answer.
Which of the following is the correct way to calculate the probability that at least 109 passengers show up to the flight?
	
	
	
	
		Resposta Selecionada:
	 
0.24 + 0.20 + 0.13 + 0.06 + 0.05 + 0.02
	Resposta Correta:
	 
Both (0.16 + 0.24 + 0.20 + 0.13 + 0.06 + 0.05 + 0.02) and (1 – 0.14) are correct.
	
	
	
Pergunta 9
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.
It was reported that 30% of all credit card users in the U.S. pay their card card bill in full every month.A random sample of size n=84 credit cards users is chosen. Which of the following is true regarding the effect of the increased sample size (from 21 to 84) on the mean and standard deviation of sampling distribution of pˆ?
	
	
	
	
		Resposta Selecionada:
	 
The mean of the sampling distribution will stay the same, but the standard deviation will decrease.
	Resposta Correta:
	 
The mean of the sampling distribution will stay the same, but the standard deviation will increase.
	
	
	
Pergunta 10
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. 
Scores of the Math portion of the SAT (SAT-M) are known to have a national mean μ=500and standard deviation σ=100.
A random sample of n=400 high-school seniors was chosen and their average SAT-M score was found to be x̅=522.
Would thisfinding surprise you? 
	
	
	
	
		Resposta Selecionada:
	 
No since an average of 522 is less than one standard deviation above 500
	Resposta Correta:
	 
Yes, since an average of 522 is more than 4 standard deviations above 500.
	
	
	
Quarta-feira, 23 de Outubro de 2019 13h42min26s BRT