Question 1

Each employee of a large company is encouraged to contribute,through payroll deduction,to an international charity.Annual contributions per employee follow (approximately)a normal distribution.You take a random sample of 25 employees and find that the sample mean annual contribution per employee is $501 with a standard deviation of $17.00.What are the boundaries for a 99% confidence interval for the population mean,rounded to two decimal places?

Accepted Answer

The answer of Each employee of a large company is...

Question 2

A random sample of 1,100 adults showed that 32% of them are smokers.Based on this sample,the 90% confidence interval for the proportion of all adults who are smokers,rounded to four decimal places,is:

Accepted Answer

The answer of A random sample of 1,100 adults showed...

Question 3

We use the t distribution to make a confidence interval for the population mean if the population from which the sample is drawn is (approximately)normally distributed,the population standard deviation is unknown,and the sample size is at least:

Accepted Answer

A) 30 
B) 100 
C) 50 
D) 2

Question 4

We are using the mean of a sample as a point estimate for the mean of a normal distribution with a standard deviation of 5.The margin of error,with 95% confidence,for this estimate is 0.860.What is the sample size?

Accepted Answer

The answer of We are using the mean of a...

Question 5

A researcher wants to estimate the mean age of all Business Week readers at a 99% confidence level.She wants the margin of error to be within 3.1 years of the population mean.The standard deviation of ages of all Business Week readers is 10.04 years.The sample size that will yield a margin of error within 3.1 of the population mean is:

Accepted Answer

The answer of A researcher wants to estimate the mean...

Question 6

The values assigned to a population parameter based on the value(s)of a sample statistic are:

Accepted Answer

A) the probabilities 
B) the probability distribution 
C) a sampling distribution 
D) estimate(s)

Question 7

Which of the following is not part of the procedure for estimating the value of a population parameter?

Accepted Answer

A) Selecting a sample 
B) Collecting the required information from the members of the sample 
C) Calculating the value of the sample statistic 
D) Calculating the exact value of the corresponding population parameter

Question 8

A t distribution has a standard deviation of  .If the standard deviation is equal to 1.1055,what is the value of the t critical value for a 90% confidence interval?

Accepted Answer

The answer of A t distribution has a standard deviation...

Question 9

Out of a sample of 639 gasoline purchases at a self-service gas station,544 were made with a credit or debit card.Obtain the predeterminated margin of error.Round your answer to three decimal places.

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The answer of Out of a sample of 639 gasoline...

Question 10

A random sample of 450 produced a sample proportion of 0.71.The 95% confidence interval for the population proportion,rounded to four decimal places,is:

Accepted Answer

The answer of A random sample of 450 produced a...

Question 11

The single value of a sample statistic that we assign to the population parameter is a:

Accepted Answer

A) single estimate 
B) unique estimate 
C) point estimate 
D) singular estimate

Question 12

A sample of size 65 from a population having standard deviation  = 55 produced a mean of 234.00.The 95% confidence interval for the population mean (rounded to two decimal places)is:

Accepted Answer

The answer of A sample of size 65 from a...

Question 13

A company wants to estimate,at a 95% confidence level,the proportion of all families who own its product.The most conservative estimate of the sample size that would limit the margin of error to be within 0.046 of the population proportion is:

Accepted Answer

The answer of A company wants to estimate,at a 95%...

Question 14

A random sample of 354 persons showed that 306 do not have health insurance.Calculate the point estimate of the population proportion of persons who do not have health insurance.Round to 4 decimal places.

Accepted Answer

The answer of A random sample of 354 persons showed...

Question 15

A scientist is estimating the mean lifetime of a newly-discovered insect.From a sample of 88 insects,she finds a sample mean of 49.2 days.Suppose that the population standard deviation of all lifetimes is 2.500 days.What are the boundaries for a 90% confidence interval for the mean lifetime of the insect,rounded to two decimal places?

Accepted Answer

The answer of A scientist is estimating the mean lifetime...

Question 16

The sample statistic used to estimate a population parameter is a(n):

Accepted Answer

A) random variable 
B) qualitative variable 
C) estimator 
D) parameter

Question 17

When making a confidence interval for the population mean using the t procedures,the degrees of freedom for the t distribution are:

Accepted Answer

A) n 
B) n - 2 
C) n + 1 
D) n - 1

Question 18

The mean IQ score of a sample of 61 students selected from a high school is 87.Suppose the standard deviation of IQ's at this school is  = 8.4.The 99% confidence interval for the population mean (rounded to two decimal places)is:

Accepted Answer

The answer of The mean IQ score of a sample...

Question 19

A random sample of 188 produced a sample proportion of 0.40.The 98% confidence interval for the population proportion,rounded to four decimal places,is:

Accepted Answer

The answer of A random sample of 188 produced a...

Question 20

The width of a confidence interval depends on the size of the:

Accepted Answer

A) population mean 
B) margin of error 
C) sample mean 
D) none of these

Exam 8: Estimation of the Mean and Proportion

A random sample of 1,100 adults showed that 32% of them are smokers.Based on this sample,the 90% confidence interval for the proportion of all adults who are smokers,rounded to four decimal places,is:

We use the t distribution to make a confidence interval for the population mean if the population from which the sample is drawn is (approximately) normally distributed,the population standard deviation is unknown,and the sample size is at least:

We are using the mean of a sample as a point estimate for the mean of a normal distribution with a standard deviation of 5.The margin of error,with 95% confidence,for this estimate is 0.860.What is the sample size?

The values assigned to a population parameter based on the value(s) of a sample statistic are:

Which of the following is not part of the procedure for estimating the value of a population parameter?

A t distribution has a standard deviation of .If the standard deviation is equal to 1.1055,what is the value of the t critical value for a 90% confidence interval?