## (CORRECT ANSWER) MATH225 Week 6 Assignment : Understanding Confidence Interval- Excel

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**1.Question**

In a city, 22 coffee shops are randomly selected, and the temperature of the coffee sold at each shop is noted. Use Excel to find the 90% confidence interval for the population mean temperature. Assume the temperatures are approximately normally distributed. Round your answers to two decimal places and use increasing order.

Ans:

**2.Question**

The yearly incomes, in thousands, for 24 random married couples living in a city are given below. Assume the yearly incomes are approximately normally distributed. Use Excel to find the 95% confidence interval for the true mean, in thousands. Round your answers to three decimal places and use increasing order.

Ans:

**3.Question**

A city is holding a referendum on increasing property taxes to pay for a new high school. In a survey of 458 likely voters, 254 said that they would vote “yes” on the referendum. Create a 95% confidence interval for the proportion of likely voters who will vote “yes” on the referendum. Use Excel to create the confidence interval, rounding to four decimal places.

Provide your answer below:

Ans:

**4.Question**

In a survey of 1,000 adults in a country, 722 said that they had eaten fast food at least once in the past month. Create a 95% confidence interval for the population proportion of adults who ate fast food at least once in the past month. Use Excel to create the confidence interval, rounding to four decimal places.

Provide your answer below:

**5.Question**

In a survey of 603 adults, 98 said that they regularly lie to people conducting surveys. Create a 99% confidence interval for the proportion of adults who regularly lie to people conducting surveys. Use Excel to create the confidence interval, rounding to four decimal places.

Provide your answer below:

Ans:

**6.Question**

Weights, in pounds, of ten-year-old girls are collected from a neighborhood. A sample of 26 is given below. Assuming normality, use Excel to find the 98% confidence interval for the population mean weight μ. Round your answers to three decimal places and use increasing order.

Ans:

**7.Question**

A company wants to determine a confidence interval for the average CPU time of its teleprocessing transactions. A sample of 70 random transactions in milliseconds is given below. Assume that the transaction times follow a normal distribution with a standard deviation of 600 milliseconds. Use Excel to determine a 98% confidence interval for the average CPU time in milliseconds. Round your answers to the nearest integer and use ascending order

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**8.Question**

Suppose the weights of tight ends in a football league are normally distributed such that σ2=1,369. A sample of 49 tight ends was randomly selected, and the weights are given below. Use Excel to calculate the 95% confidence interval for the mean weight of all tight ends in this league. Round your answers to two decimal places and use ascending order

Ans.

**9.Question**

A sample of 22 test-tubes tested for number of times they can be heated on a Bunsen burner before they crack is given below. Assume the counts are normally distributed. Use Excel to construct a 99% confidence interval for μ. Round your answers to two decimal places and use increasing order.

Ans.

**10.Question**

In a random sample of 350 attendees of a minor league baseball game, 184 said that they bought food from the concession stand. Create a 95% confidence interval for the proportion of fans who bought food from the concession stand. Use Excel to create the confidence interval, rounding to four decimal places.

Ans:

**11.Question**

Alison, the owner of a regional chain of pizza stores, is trying to decide whether to add calzones to the menu. She conducts a survey of 700 people in the region and asks whether they would order calzones if they were on the menu. 46 people responded “yes.” Create a 90% confidence interval for the proportion of people in the region who would order calzones if they were on the menu. Round your answer to four decimal places.

Ans.

**12.Question**

A tax assessor wants to assess the mean property tax bill for all homeowners in a certain state. From a survey ten years ago, a sample of 28 property tax bills is given below. Assume the property tax bills are approximately normally distributed. Use Excel to construct a 95% confidence interval for the population mean property tax bill. Round your answers to two decimal places and use increasing order.

Ans.

**13.Question**

The following data represent a sample of the assets (in millions of dollars) of 28 credit unions in a state. Assume that the population in this state is normally distributed with σ=3.5 million dollars. Use Excel to find the 99% confidence interval of the mean assets in millions of dollars. Round your answers to three decimal places and use ascending order.

Ans.

**14.Question**

The monthly incomes from a random sample of 20 workers in a factory is given below in dollars. Assume the population has a normal distribution and has standard deviation $518. Compute a 98% confidence interval for the mean of the population. Round your answers to the nearest dollar and use ascending order

**Monthly Income**

11621

12367

12030

12135

12561

11453

12313

11561

12424

Cont……

Thus, the 98% confidence interval for μ, rounded to the nearest integer, is

**15.Question**

A study was conducted to estimate the mean age when people buy their first new car. The ages of purchase for 22 randomly selected people are given below. Assume the ages are approximately normally distributed. Use Excel to determine the 99% confidence interval for the mean. Round your answers to two decimal places and use increasing order

**Age**

19

25

27

23

15

21

22

15

18

Cont……

Thus, the 99% confidence interval for the mean is

**16.Question**

A type of golf ball is tested by dropping it onto a hard surface from a height of 1 meter. The height it bounces is known to be normally distributed. A sample of 25 balls is tested and the bounce heights are given below. Use Excel to find a 95% confidence interval for the mean bounce height of the golf ball. Round your answers to two decimal places and use increasing order

**Height**

81.4

80.8

84.4

85.6

82.9

76.0

80.0

83.2

80.8

Cont……

95% confidence interval will be:

**17.Question**

In a random sample of 2,282 college students, 356 reported getting 8 or more hours of sleep per night. Create a 95% confidence interval for the proportion of college students who get 8 or more hours of sleep per night. Use Excel to create the confidence interval, rounding to four decimal places.

Thus, the 95% confidence interval for the population proportion of college students who get 8 or more hours of sleep per night, based on this sample, is approximately

**18.Question**

A large company is concerned about the commute times of its employees. 333 employees were surveyed, and 131 employees said that they had a daily commute longer than 30 minutes. Create a 95% confidence interval for the proportion of employees who have a daily commute longer than 30 minutes. Use Excel to create the confidence interval, rounding to four decimal places.

Thus, the 95% confidence interval for the population proportion of employees who have a daily commute longer than 30 minutes , based on this sample, is approximately

**19.Question**

A restaurant is reviewing customer complaints. In a sample of 227 complaints, 57 complaints were about the slow speed of the service. Create a 95% confidence interval for the proportion of complaints that were about the slow speed of the service. Use Excel to create the confidence interval, rounding to four decimal places.

Provide your answer below:

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