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A study of rush-hour traffic in San Francisco counts the number of people in each car entering a freeway at a suburban interchange. Suppose that this count has mean 1.6 and standard deviation 0.75 in the population of all cars that enter at this interchange during rush hour.

a. Without doing any calculations, explain which event is more likely:

  • randomly selecting 1 car entering this interchange during rush hour and finding 2 or more people in the car
  • randomly selecting 35 cars entering this interchange during rush hour and finding an average of 2 or more people in the cars

b. Explain why you cannot use a Normal distribution to calculate the probability of the first event in part (a).

c. Calculate the probability of the second event in part (a).

Short Answer

Expert verified

a. Choosing one automobile at random when it enters the interchange during rush hour and finding two or more passengers in it

b. The sample size is tiny, and the population distribution is uncertain.

c. The resultant probability of part(a) is 0.04%

Step by step solution

01

Part (a) Step 1: Given Information

The mean is 1.6 and standard deviation is 0.75

02

Part (a) Step 2: According to the given question

The population standard deviation divided by the square root of sample size equals the standard deviation of the sampling distribution of the sample mean.

σx¯=σn

As a result, the standard deviation lowers as the sample size grows, and the data values become closer to the predicted value as the sample size grows.

This means that when the sample size is bigger, you are less likely to find a mean of two or more individuals in the automobiles, and hence an occurrence with a smaller sample size (1 car) is more likely to occur.

03

Part (b) Step 1: Given Information

The mean is 1.6 and standard deviation is 0.75

04

Part (b) Step 2: According to the given question

n=1

The centre limit theorem states that if the sample size is more than 30, the sampling distribution of the sample mean x¯is approximately normal.

The central limit theorem cannot be applied since the sample size of 1 is less than 30. The sample mean sampling distribution has the same shape as the population distribution in this example.

Although the population distribution is unknown, the form of the sampling distribution of the sample mean is also unknown, which means that the probability cannot be calculated.

05

Part (c) Step 1: Given Information

The mean is 1.6 and standard deviation is 0.75

06

Part (c) Step 2: According to the given question

Consider that,

μ=1.6σ=0.75n=40x¯=2

The following concept was used:

z=x−μx¯σx¯

So, the z-score is

localid="1657533591800" role="math" z=2−1.60.7540=3.37

The z-two score's found expressions must then be equal: P(Z<3.37)is standard distribution of the sample mean is roughly normal, as shown in the row beginning with 3.3 and the column beginning with.07.

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Most popular questions from this chapter

Suppose we select an SRS of size n=100n=100from a large population having proportion p of successes. Let p∧p^be the proportion of successes in the sample. For which value of p would it be safe to use the Normal approximation to the sampling distribution of p∧p^?

a. 0.01

b. 0.09

c. 0.85

d. 0.975

e. 0.999

In a certain large population of adults, the distribution of IQ scores is strongly left skewed with a mean of 122 and a standard deviation of 5. Suppose 200 adults are randomly selected from this population for a market research study. For SRSs of size 200, the distribution of sample mean IQ score is

a. left-skewed with mean 122 and standard deviation 0.35.

b. exactly Normal with mean 122 and standard deviation 5.

c. exactly Normal with mean 122 and standard deviation 0.35.

d. approximately Normal with mean 122 and standard deviation 5.

e. approximately Normal with mean 122 and standard deviation 0.35.

The distribution of scores on the mathematics part of the SAT exam in a recent year was approximately Normal with mean 515 and standard deviation 114 . Imagine choosing many SRSs of 100 students who took the exam and averaging their SAT Math scores. Which of the following are the mean and standard deviation of the sampling distribution of x-?x¯?

a. Mean =515,SD=114

b. Mean =515,SD=114/100SD=114/100

c. Mean role="math" localid="1654342976765" =515/100,SD=114/100

d. Mean role="math" localid="1654343050312" =515/100,SD=114/100SD=114/10

e. Cannot be determined without knowing the 100 scores.

The distribution of grade point average for students at a large high school is skewed to the left with a mean of 3.53 and a standard deviation of 1.02.

a. Describe the shape of the sampling distribution of x¯ for SRSs of size n = 4 from the population of students at this high school. Justify your answer.

b. Describe the shape of the sampling distribution of x¯ for SRSs of size n = 50 from the Page Number: 480 population of students at this high school. Justify your answer.

Suppose we roll a fair die four times. What is the probability that a 6 occurs on exactly one of the rolls?

a.4(16)3(56)14163561b.(16)3(56)1163561c.4(16)1(56)3161563d.(16)1(56)3161563e.6(16)1(56)36161563

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