For a study conducted by the research department of a pharmaceutical company, 240 randomly selected individuals were asked to report the amount of money thay spend annually on prescription allergy relief medication. The sample mean was found to be $17.60, with a standard deviation of $5.50.
A random sample of 245 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 $18.40, with a standard deviation of $4.30. As the sample sizes were quite large, it was assumd that the respective population standard deviations of the spending for prescription and non-prescription allergy relief medication could be estimated by the respective sample standard deviation values given above.
Construct a 95% confidence interval for the difference µ1 - µ2 between the mean spending on prescription allergy relief medication (µ1) and the mean spending on non-prescription allergy relief medication (µ2).