Exam 9: Sampling Distributions and Confidence Intervals for Proportions

A men's clothing store has determined the following probability distribution for the number of special size orders placed per month. Based on this distribution, the standard Deviation in the number of special size orders placed per month is

A researcher is conducting a study on eating disorders. Using a list of recent participants in the online Weight Watchers program, she randomly selects a name from The alphabetized list. She then chooses every tenth person from that point on to include In her study. This sampling strategy is called

A recent poll of 120 adults who frequent the local farmer's market found that 54 have purchased reusable cloth bags for their groceries. Based on these data, what is the margin Of error for a 95% confidence interval of the proportion of adults who have purchased Reusable cloth bags?

Which is true about a 99% confidence interval based on a given sample? I. The interval contains 99% of the population. II) Results from 99% of all samples will lie in this interval. III) The interval is wider than a 95% confidence interval would be.

Suppose that the store chain of Electronics Plus sells extended warranties to 20% of customers who purchase electronic devices. A local Seattle store samples 300 customers from their data base. A. What proportion of customers would they expect to have purchased extended warranties? b. What is the standard deviation of the sample proportion? c. What shape would you expect the sampling distribution of the proportion to have? d. Would you be surprised to find out that in a sample of 300, 40 of the customers purchased extended warranties? Explain. What might account for this high percentage?

The Quality Control Department wants to estimate the true percentage of rework for electrical components to within ±4%, with 99% confidence. Based on similar past Studies, the percentage of rework was found to be 12%. How many components should They sample?

The U.S. Department of Labor wants to estimate the percentage of females in the labor force to within ±2% 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?

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. The standard Deviation of the sampling distribution of mean times is

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. The Quality Control Department plans to check a random sample of the over 10,000 electrical components Manufactured across all divisions. The resulting 95% confidence interval based on these Data is .0758 to .1339. Which of the following is the correct interpretation?

Which of the following is not an assumption and/or condition required for constructing a confidence interval for the proportion?

A government agency has 6000 employees. As an alternative to the traditional five day work week, employees were asked whether they preferred a four day work week (10 Hours per day) or flexible hours. The table below shows the results by age category. What is the probability that an employee at this government agency prefers a four day Work week? Age Category Prefers 4 Day Week Prefers Flex Hours Under 30 600 300 30-45 1200 1500 Over 45 2100 300

The unemployment rate of persons with a disability is typically higher than for those with no disability. Recent statistics report that the national rate of unemployment among This group is 14.5%. The local government of a small city wants to determine the rate in Its region to within ±5%, with 95% confidence. How many individuals with disabilities Should they sample?

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 select a random Sample of 525 from over 10,000 employment records on file and find that 229 are female. The 90% confidence interval for the proportion of females in the U.S. labor force is

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 between 80 and 96.

Grandma Gertrude's Chocolates, a family owned business, has an opportunity to supply its product for distribution through a large coffee house chain. However, the coffee house chain has certain specifications regarding cacao content as it wishes to advertise the health benefits (antioxidants) of the chocolate products it sells. In order to determine the mean % cacao in its dark chocolate products, quality inspectors sample 36 pieces. They find a sample mean of 55% with a standard deviation of 4%. A. Describe the sampling distribution for the sample mean. b. What is the standard error? c. What is the margin of error for 90% confidence? d. What is the margin of error for 95% confidence? e. Based on the sample results, find the 90% confidence interval and interpret. f. Based on the sample results, find the 95% confidence interval and interpret. g. For a more accurate determination of the mean weight, the quality control inspectors wish to estimate it within 1% with 95% confidence. How many pieces of dark chocolate should they sample?

Recent statistics report that the national rate of unemployment among persons with disabilities is 14.5%. The local government of a small city samples 200 individuals with Disabilities and finds that 44 are unemployed. The 99% confidence interval for the Unemployment rate among persons with disabilities in their city is

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 between 64 and 88.

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. What is the margin of error for a 99% confidence interval based on These sample results?

A researcher is conducting a study to determine how knowledgeable teenagers are about making good food choices. She decides to interview teenagers eating at a fast food Restaurant. The results may be biased because this is a

A survey of investors finds that 60% use a full service brokerage firm to invest in stocks, 30% trade stocks online and 24% do both. The probability that an investor Selected at random uses a full service brokerage firm or trades stocks online is