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A market survey has shown that people will spend an average of $2.34 each for your product next year, based on a sample survey of 400 people.
Find the two-sided 95% confidence interval for the percent dissatisfied among all of your customers (i.e, not just those surveyed).
Find the two-sided 95% confidence interval for the mean length of coils in the larger population. Write a brief paragraph explaining its meaning.
As a basis for a brochure describing the speed of a new computer system, you have measured how long it takes the machine to complete a particular benchmark.
Identify the population and the population mean. Why is the population mean important to the management and owners of the proposed mine?
Express your confidence interval in terms of pounds per year, assuming operations continue 365 days/year.
If the distribution of sales prices is heavily skewed, would it be appropriate to construct the usual two-sided 95% confidence interval? Why or why not?
A random sample of 50 recent patient records at a clinic shows that the average billing per visit was $53.01 and the standard deviation was $16.48.
Click-through rates were measured for each of 83 mobile advertising campaigns, and showed an average rate of 2.38%, with a standard error of 0.134%.
Find the two-sided 95% confidence interval for the mean weight you would have found had you weighed all packages produced today.
Your hospital is negotiating with medical insurance providers, who would like to reduce the amount they pay as reimbursement for hospital stays.
Your quality control department has just analyzed the contents of 20 randomly selected barrels of materials to be used in manufacturing plastic garden equipment
The average score was 4.125, the standard error was 0.1099, and the 95% confidence interval extended from 3.904 to 4.346. Find the margin of error.
A random sample of eight customers was interviewed in order to find the number of computers they planned to order next year.
View the 989 donors in the donations database (out of 20,000 people represented on the companion site) as a random sample from a much larger population.
View the 20,000 people represented in the donations database (on the companion site) as a sample from a much larger population.
Find the one-sided 99% confidence interval that claims that the population mean for this cost is no larger than some amount.
Your bakery produces loaves of bread with “1 pound” written on the label. Here are weights of randomly sampled loaves from today’s production.
Find the two-sided 95% confidence interval for next year’s mean expenditure per person in the larger population.
Approximately how far is the average of these 12 quotes from the unknown mean for the entire population of providers?
Find the 95% confidence interval for the percentage of the population of regular readers who would express such interest in buying the new product.
A recent survey of 252 customers, selected at random from a database with 12,861 customers, found that 208 are satisfied.
In a sample of 258 individuals selected randomly from a city of 750,339 people, 165 were found to be supportive of a new public works project.
What does a confidence interval tell you about the population that an estimated value alone does not?
Why is it correct to say, “We are 95% sure that the population mean is between $15.85 and $19.36” but not proper to say.