10-50. As the number of air travelers with time on their hands increases, it would seem that spending on retail purchases in airports would increase as well.

A study by Airport Revenue News addressed the per person spending at selected airports for merchandise, excluding food, gifts, and news items. A file entitled Revenues contains sample data selected from

airport retailers in 2005 and again in 2008.

a.     Conduct a hypothesis test to determine if the average amount of retail spending by air travelers has increased as least as much as approximately

$0.10 a year from 2005 to 2008. Use a significance level of 0.025.

b.    Using the appropriate analysis (that of part a or other appropriate methodology), substantiate the statement that average retail purchases in airports increased over the time period between 2005 and 2008. Support your assertions.

c.                                 Parts a and b give what seems to be a mixed message. Is there a way to determine what values are plausible for the difference between the average revenue in 2005 and 2008? If so, conduct the appropriate procedure.

 

 

Skill Development

10-51. In each of the following cases, determine if the sample sizes are large enough so that the sampling distribution of the differences in the sample proportions can be approximated with a normal distribution:

a.  n1 = 15, n2 = 20, x1 = 6, and x2 = 16 b. n1 = 10, n2 = 30, p1 = 0.6, and x2 = 19 c.  n1 = 25, n2 = 16, x1 = 6, and p2 = 0.40

d. n1 = 100, n2 = 75, p1 = 0.05, and p2 = 0.05

10-52. Given the following sample information randomly

selected from two populations

 

 

 

 

 

 

Sample 1          Sample 2

 

n1= 200            n2 = 150

x1= 40              x2 = 27

 

a.     Determine if the sample sizes are large enough so that the sampling distribution for the difference between the sample proportions is approximately normally distributed.

b.    Calculate a 95% confidence interval for the difference between the two population proportions.