Long 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?

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.)