Exam 9: Sampling Distributions and Confidence Intervals for Proportions

One division of a large defense contractor manufactures telecommunication equipment for the military. This division reports that 12% of non-electrical components Are reworked. Management wants to determine if this percentage is the same as the Percentage rework for the company's electrical components. Based on a random sample Of 450 electrical components, they find that 46 had to be reworked. The 99% confidence Interval is

Suppose the time it takes for a purchasing agent to complete an online ordering process is normally distributed with a mean of 8 minutes and a standard deviation of 2 Minutes. Suppose a random sample of 25 ordering processes is selected. What is the Probability that the sample mean will be less than 7.5 minutes?

EU (European Union) countries report that 46% of their labor force is female. The United Nations wants to determine if the percentage of females in the U.S. labor force is The same. Based on a sample of 500 employment records, representatives from the United States Department of Labor find that the 95% confidence interval for the Proportion of females in the U.S. labor force is .357 to .443. Which of the following is the Correct interpretation?

The number of claims for lost luggage in a small city airport averages nine per day. Assuming the Poisson distribution, what is the probability that there will be fewer than 3 Claims on any given day?

A human resources manager at a large company wants to estimate the proportion of employees that would be interested in reimbursement for college courses. If she wishes To be 95% confident that her estimate is within 5% of the true proportion, how many Employees would need to be sampled?

A large software development firm recently relocated its facilities. Top management is interested in fostering good relations with their new local community and has encouraged their professional employees to engage in local service activities. They wish to determine the average number of hours the firm's professionals volunteer per month. A random sample of 24 professionals reported the following number of hours: 12 13 14 14 15 15 15 16 16 16 16 16 17 17 17 18 18 18 18 19 19 19 20 21 A. Based on the sample results, find the 95% confidence interval and interpret. b. For a more accurate determination, top management wants to estimate the average number of hours volunteered per month by their professional staff to within one hour with 99% confidence. How many randomly selected professional employees would they need to sample? c. Suppose 40 professional employees are randomly selected. This sample yields a mean of 15.2 hours and a standard deviation of 1.8 hours. Find a 95% confidence interval and interpret.

Automobile mechanics conduct diagnostic tests on 150 new cars of particular make and model to determine the extent to which they are affected by a recent recall due to Faulty catalytic converters. They find that 42 of the new cars tested do have faulty Catalytic converters. The 99% confidence interval for the true proportion of new cars With faulty catalytic converters is

The U.S. Department of Labor wants to estimate the percentage of females in the labor force to within ±5% with 90% confidence. As a planning value they use 46%, the Reported percentage of females in the labor force of EU (European Union) countries. How many employment records should be sampled?

A Normal probability plot of the weights of individuals signed up for a popular diet program is shown below. The best description of the plot is

All else being equal, increasing the level of confidence desired will

As a result of the financial crisis on Wall Street in September 2008 that required federal government intervention, a survey showed that 40% of Americans reallocated Their investments to reduce exposure to the stock market. What is the probability that out Of 5 randomly selected Americans, none will have reallocated their investments in this Way?

We have calculated a 95% confidence interval and would like our next confidence interval to have a smaller margin of error without losing any confidence. In order to do This, we can I. change the z∗ value to a smaller number. II. take a larger sample. III. take a smaller sample.

A manufacturer of cheese filled ravioli supplies a pizza restaurant chain. Based on data collected from its automatic filling process, the amount of cheese inserted into the ravioli is normally distributed. To make sure that the automatic filling process is on target, quality control inspectors take a sample of 25 ravioli and measure the weight of cheese filling. They find a sample mean weight of 15 grams with a standard deviation of 1.5 grams. A. Describe the sampling distribution for the sample mean. b. What is the standard error? c. What is the margin of error for 99% confidence? d. What is the margin of error for 90% confidence? e. Based on the sample results, find the 99% confidence interval and interpret. f. Based on the sample results, find the 90% confidence interval and interpret. g. For a more accurate determination of the mean weight, the quality control inspectors wish to estimate it within .25 grams with 99% confidence. How many ravioli should they sample?

Assume that a set of test scores in an Introduction to Finance class is normally distributed with a mean of 72 and a standard deviation of 8. Use the 68-95-99.7 rule to Find the percentage of scores greater than 88.

EU (European Union) countries report that 46% of their labor force is female. The United Nations wants to determine if the percentage of females in the U.S. labor force is The same. Based on a sample of 500 employment records, representatives from the United States Department of Labor find that 240 are female. What is the margin of error For the 95% confidence interval of the proportion of females in the U.S. labor force?

If a parameter is computed from a set of data, which of the following statements is true?

A manufacturer of batteries routinely tests its products to determine lifetime (hours of continuous usage). Suppose they select a sample of 30 AAA batteries and find that the Average lifetime is 1500 hours. This is a

Speeds of cars were measured as they passed one point on a road to study whether traffic speed controls were needed. Here's a histogram and boxplot of the measured Speeds. Accurate statements about this distribution include.

Nine out of 25 randomly selected Students of WMU live in Southwest Michigan. The result says that the true proportion could be as low as 0.17 or as high as 0.55. If we Want to reduce the margin of error from 0.19 to 0.10. Using the estimate of 0.36 based on The initial sample, what sample size would be needed to achieve the reduced margin of Error?

EU (European Union) countries report that 46% of their labor force is female. The United Nations wants to determine if the percentage of females in the U.S. labor force is the same. Representatives from the United States Department of Labor plan to check a random sample of over 10,000 employment records on file to estimate the percentage of females in the U.S. labor force. A. The Department of Labor wants to estimate the percentage of females in the U.S. labor force to within ±5%, with 90% confidence. How many employment records should be sampled? b. They actually select a random sample of 525 employment records, and find that 229 of the people are females. Construct the 90% confidence interval. c. Interpret the confidence interval in this context. d. Explain what 90% confidence means in this context. e. Should representatives from the Department of Labor conclude that the percentage of females in the U.S. labor force is lower than Europe's rate of 46%? Explain. f. Are the assumptions and conditions for constructing a confidence interval met? Explain.