Table 7.6: Annual Salaries Uncertified CPA Average $48,500 $56,600 SD $8,700 $9,100 Sample Size 4 6 7.25. A clothing company wanted to compare the service satisfaction of two of their retail stores. Customers were asked to rate the service they received on a scale of 1 to 10. A survey was conducted on 150 customers visiting their NYC store, who recorded an average rating of 7.4 with a standard deviation of 1.3. The similar survey was conducted on 200 customers visiting their Chicago store, yielding an average rating of 8.2 and a standard deviation of 1.8. Develop and interpret a 90% confidence interval estimate for the difference between mean ratings of the two stores