BackLong Life? In a survey of 35 adult Americans, it was found that the mean age (in years) that people would like to live to is 87.9 with a standard deviation of 15.5. An analysis of the raw data indicates the distribution is skewed left.
c. How many adult Americans would need to be surveyed to estimate the mean age that people would like to live to within 2 years with 95% confidence?
A puzzle company is interested in the average number of pieces in their jigsaw puzzles, so they plan to create a confidence interval for the true mean. The easiest puzzle in their line is pieces, and the largest is pieces. Use the range rule of thumb to estimate the sample standard deviation.
A bookstore is interested in the average length of books in its adult fiction section. Find the minimum sample size required to create a confidence interval with a margin of error no more than pages if...
(A) The standard deviation is known to be about pages.
A bookstore is interested in the average length of books in its adult fiction section. Find the minimum sample size required to create a confidence interval with a margin of error no more than pages if...
(B) The standard deviation is unknown, but the longest book is pages and the shortest is pages.
A simple random sample of size n is drawn from a population that is normally distributed. The sample mean, x̄, is found to be 108, and the sample standard deviation, s, is found to be 10.
b. Construct a 96% confidence interval for μ if the sample size, n, is 10. How does decreasing the sample size affect the margin of error, E?
Reading A recent Gallup poll asked Americans to disclose the number of books they read during the previous year. Initial survey results indicate that s = 16.6 books.
a. How many subjects are needed to estimate the number of books Americans read the previous year within four books with 95% confidence?
Reading A recent Gallup poll asked Americans to disclose the number of books they read during the previous year. Initial survey results indicate that s = 16.6 books.
b. How many subjects are needed to estimate the number of books Americans read the previous year within two books with 95% confidence?
Reading A recent Gallup poll asked Americans to disclose the number of books they read during the previous year. Initial survey results indicate that s = 16.6 books.
c. What effect does doubling the required accuracy have on the sample size?
Reading A recent Gallup poll asked Americans to disclose the number of books they read during the previous year. Initial survey results indicate that s = 16.6 books.
d. How many subjects are needed to estimate the number of books Americans read the previous year within four books with 99% confidence? Compare this result to part (a). How does increasing the level of confidence in the estimate affect sample size? Why is this reasonable?
Television A researcher wanted to determine the mean number of hours per week (Sunday through Saturday) the typical person watches television. Results from the Sullivan Statistics Survey I indicate that s = 7.5 hours.
a. How many people are needed to estimate the number of hours people watch television per week within 2 hours with 95% confidence?
Television A researcher wanted to determine the mean number of hours per week (Sunday through Saturday) the typical person watches television. Results from the Sullivan Statistics Survey I indicate that s = 7.5 hours.
c. What effect does doubling the required accuracy have on the sample size?
Television A researcher wanted to determine the mean number of hours per week (Sunday through Saturday) the typical person watches television. Results from the Sullivan Statistics Survey I indicate that s = 7.5 hours.
d. How many people are needed to estimate the number of hours people watch television per week within 2 hours with 90% confidence? Compare this result to part (a). How does decreasing the level of confidence in the estimate affect sample size? Why is this reasonable?
Population A has standard deviation σA = 5, and population B has standard deviation σB = 10. How many times larger than Population A’s sample size does Population B’s need to be to estimate μ with the same margin of error? (Hint: Compute nB/nA.)
Television A researcher wanted to determine the mean number of hours per week (Sunday through Saturday) the typical person watches television. Results from the Sullivan Statistics Survey I indicate that s = 7.5 hours.
b. How many people are needed to estimate the number of hours people watch television per week within 1 hour with 95% confidence?
True or False: The distribution of the sample mean, x̄, will be approximately normally distributed if the sample is obtained from a population that is not normally distributed, regardless of the sample size.