Cond Nast Traveler conducts an annual survey in which readers rate their favorite cruise ship. All ships are rated on a 100-point scale, with higher values indicating better service. A sample of ships that carry fewer than 500 passengers and a sample of ships that carry 500 or more passengers is provided in the Microsoft Excel Online file below (Cond Nast Traveler, February 2008).

Round your all answers to two decimal places.

a. What is the point estimate of the difference between the population mean rating for ships that carry fewer than 500 passengers and the population mean rating for ships that carry 500 or more passengers?

b. At 95% confidence, what is the margin of error?

c. What is a 95% confidence interval estimate of the difference between the population mean ratings for the two sizes of ships?

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Smaller Ships	Larger Ships
94.4	81.9
84.11	85.67
87.48	83.52
83.06	88.79
92.5	79
72.96	82.81
77.41	80.93
85.78	74.96
80.77	91.72
89.9	78
85.45	82.73
86.53	81.63
80.84	89.23
88.14	77.82
86.2	91.6
83.37	85.14
89.38	83.74
75.57	76.82
76.55	76.63
75.33	81.2
85.61	82.33
90.97	74.93
89.18	78.63
88.05	74.91
93.81	83.08
83.33	74.95
89.84	81.86
81.78	81.36
86.21	87.81
91.4	85.18
72.74	86.88
90.37	74.85
76.99	75.21
79.67	81.72
84.61	82.75
84.8	86.59
85.92	75.24
	86.33
	80.44
	83.87
	81.54
	85.7
	78.81
	79.53