Question

For a study conducted by the research department of a pharmaceutical company,

280

randomly selected individuals were asked to report the amount of money they spend annually on prescription allergy relief medication. The sample mean was found to be

$17.50

with a standard deviation of

$5.30

. A random sample of

275

individuals was selected independently of the first sample. These individuals reported their annual spending on non-prescription allergy relief medication. The mean of the second sample was found to be

$18.50

with a standard deviation of

$4.40

. As the sample sizes were quite large, it was assumed that the respective population standard deviations of the spending for prescription and non-prescription allergy relief medication could be estimated as the respective sample standard deviation values given above. Construct a

99%

confidence interval for the difference

−μ1μ2

between the mean spending on prescription allergy relief medication (

μ1

) and the mean spending on non-prescription allergy relief medication (

μ2

). Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.)

What is the lower limit of the 99% confidence interval? What is the upper limit of the 99% confidence interval?

Answer 1