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# Confidence Interval

### A processor of carrots cuts the green top off each carrot, washes the carrots and inserts six to a package.

A processor of carrots cuts the green top off each carrot, washes the carrots and inserts six to a package. Twenty packages are inserted in a box for shipment. To test the weight of the boxes a few were checked. The mean weight was 20.4 pounds the standard deviation 0.5 pounds. How many boxes must the processor sample to be 95 p

### The American sugar producers association wants to estimate the mean yearly sugar consumption.

The American sugar producers association wants to estimate the mean yearly sugar consumption. A sample of 16 people reveals the mean yearly consumption to be 60 pounds with a standard deviation of 20 pounds. a) What is the value of the population mean? What is the best estimate of this value? b) Explain why we need to use th

### Confidence interval normal probability and Hypothesis testing problems

1) The length of time to do a complete full service oil change at Speedy-Lube, is normally distributed with a mean of 15.8 minutes and a standard deviation of 2.2 minutes. Refer to the following table. Table 5A Below normal distribution p(lower) p(upper) z x mean std.dev .0042 .9958 -2.64 10 15.8 2.2 .9719 .0281 1.91 20

### Confidence Interval for GPA of Students

The GPA's for 10 randomly selected students are listed below. Construct a 90% confidence interval for the population standard deviation. Assume the data are normally distributed. 2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 .8 a. 1.10, 2.01 b. .32, .85 c. .53, 1.01 d. .81, 1.83

### Proportion of Students on Financial Aid

A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. Use a 99% confidence interval to estimate the true proportion of stud

### Assume that the heights of women are normally distributed.

Assume that the heights of women are normally distributed. A random sample of 20 women have a mean height of 62.5 inches and a standard deviation of 1.3 inches. Construct a 98% confidence interval for the population variance, (lower case sigma)2. a.(0.9,2.1) b.(0.9,4.4) c.(0.7,3.2) d.(0.9,4.2)

### Construct a 90% Confidence Interval for the Population Mean

Construct a 90% confidence interval for the population mean. Assume the population has a normal distribution. A sample of 15 randomly selected students has a grade point average of 2.86 with a standard deviation of 0.78. a. (2.37, 3.56) b. (2.51, 3.21) c. (2.41, 3.42) d. (2.28, 3.66).

### Confidence Level Determination

Your hospital has 500 patient - you sample 100 regarding quality of care - 74 are in favor. Data assumed to be normally distributed. Use this sample data to predict population proportion and to do so with 98% confidence (finite correction factor) a. what is the upper limit for a 99% confidence interval?

### Confidence interval, sample median, third quartile, test of hypothesis, true mean,

1. Post-It notepads have an unusual adhesive that must be strong enough to stick, but weak enough to not tear the paper when pulled to release. Several batches of adhesives were tested for consistency. Adhesiveness is measured in ounces per square inch (osi). Measurements from six batches of adhesives are given below. Assume the

### Among 100 people randomly chosen in a survey, exactly 10 stated that they believed that the elected representatives are honest most of the time.

Among 100 people randomly chosen in a survey, exactly 10 stated that they believed that the elected representatives are honest most of the time. The approximate 99% confidence interval for the percentage of the population who believe that such people are honest most of the time is?

### Testing a Hypothesis and Confidence Interval

1. The American Sugar Producers Association wants to estimate the mean yearly sugar consumption. A sample of 16 people reveals the mean yearly consumption to be 60 pounds with a standard deviation of 20 pounds. A. What is the value of the population mean? What is the best estimate of this value? B. Explain why we need to use

### A 90% confidence interval for the mean percentage of reservations being canceled on the day of the flight is (3.6%, 6.1%).

A 90% confidence interval for the mean percentage of reservations being canceled on the day of the flight is (3.6%, 6.1%). What is the point estimator of the mean percentage of reservations that are canceled on the day of the flight?

### Three multiple choice questions about confidence intervals, sample size, and hypothesis tests.

I would like to check my responses to the 3 matching questions for my homework assignment. Bus stats 7 homework 1) The width of a confidence interval will be: Choices: Narrower for 98% confidence than for 90% confidence Wider for a sample size of 64 than for a sample size of 36 Wider for a 99% confidence than for 95%

### Confidence Interval: Lower Bound

A sample of 14 joint specimens of a particular type gave a same mean proportional limit stress of 8.48 MPa and sample standard deviation of 0.79 MPa. a) Calculate and interpret a 95% lower confidence bound for the true average proportional limit stress of all such joints. What, if any assumption did you make about the distri

### What is the 90% confidence interval for the average days worked, population mean, of all payroll departments

A sample of 25 different payroll departments found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90% confidence interval for the average days worked, population mean, of all payroll departments?

### 95% confidence interval for the mean age

An economics professor randomly selected 100 millionaires in the United States. The average age of these millionaires was 54.8 years with a standard deviation of 7.9 years. What is the 95% confidence interval for the mean age, poplulation mean of all United States millionaires?

### What is the 99% confidence interval of the true mean number of miles driven by all truckers?

The average number of miles that 90 truckers drove in a day was 540.0 with a standard deviation of 40 miles. What is the 99% confidence interval of the true mean number of miles driven by all truckers? Enter the response as (beginning of interval, ending of interval) with no spaces between numbers or symbols, EXCEPT after t

### Calculating a Confidence Interval

What information is necessary to calculate a confidence interval? Is the size of the population relevant when one is determining the sample size for a confidence interval? What is necessary to determine the sample size?

### Point estimate and Interval Estimate of a Parameter

Explain the difference between a point estimate and an interval estimate of a parameter? Which is better? Why?

### The Solution to Confidence Interval for Mean

A sample of the math test scores of 35 fourth-graders has a mean of 82 with a standard deviation of 15. Find the 95% confidence interval of the mean math test scores of all fourth-graders. Find the 99% confidence interval of the mean math test scores of all fourth-graders. Which interval is larger? Explain why.

### A researcher is interested in estimating the average salary of fire fighters in a large city.

A researcher is interested in estimating the average salary of fire fighters in a large city. He wants to be 95% confident that his estimate is correct. If the standard deviation is \$1050, how large a sample is needed to get the desired information and to be accurate within \$200?

### Confidence Interval Estimate Between Means

Confidence interval for Data1 & Data2. Using the following data, construct a 95% confidence level interval estimate for the difference between the mean of Data1 and Data2. Data 1 Data 2 n1= 70.0 73 X-bar = 413.5 403.7 s 38.5 30.4

### What does a confidence interval tell us about our population?

What does a confidence interval tell us about our population?

### The International Air Transport Association surveys business travelers to develop quality ratings for transatlantic gateway airports.

Please show work. The International Air Transport Association surveys business travelers to develop quality ratings for transatlantic gateway airports. The maximum possible rating is 10. Suppose a simple random sample of 50 business travelers is selected and each traveler is asked to pro-vide a rating for the Miami Internatio

### Confidence Interval for Mean GPA

The undergraduate grade point average (GPA) for students admitted to the top graduate business schools was 3.37 (Best Graduate Schools, U.S. News and World Report, 2001). Assume this estimate was based on a sample of 120 students admitted to the top schools. Using past years Õdata, the population standard deviation can be a

### A 95% confidence interval (a t interval) for the lives (in minutes) of Kodak AA batteries is 440 < u < 480. Assume that this result is based on a sample of size 25.

Dear Ota, Provide me the solution with explanation. Thanks 1. A 95% confidence interval (a t interval) for the lives (in minutes) of Kodak AA batteries is 440 < u < 480. Assume that this result is based on a sample of size 25. 1a. What is the value of the sample mean? a. 455 b. 440 c. 445 d. 460 e.