As a marketing manager, Nathan is facing some issues. One issue that bothers Nathan is that he observes fewer female visitors patronizing the store lately; in contrast, more male visitors come and shop at the department store. Another issue is that sales in some departments, such as children and ladies clothing have declined. There are 5 departments in the store: ladies clothing, men clothing, children clothing, shoes, and accessories. Nathan is challenged to develop an effective marketing strategy to for the department store. Before making decisions, Nathan considers analyzing some customers' data. In September 2018, the marketing research unit collected customer satisfaction data. This data has always been collected in September every year. The satisfaction data have always been broken down by demographics, such as gender, age, and income. The satisfaction level is measured using a 7-point Likert scale (1=extremely dissatisfied; 7=extremely satisfied). Nathan is certain that this year's satisfaction level is over 5.

Other than satisfaction data, the research department also collected annual sales data, number of visitors' data, and number of purchased items. Nathan has some questions in mind, but he does not know how to use and analyze the data properly. The followings are Nathan's questions, and each might need different analysis:

a. Is it true that the customer satisfaction level is over 5 this year?

b. Is it true that the customer satisfaction score is significantly higher this year than last year?

c. Is it true that less female customers visit the store in comparison to the male customers this year?

d. Is it true that shoes and accessories departments' sales are significantly lower than the sales of the rest of the departments?

With all this information in hand, please help Nathan to choose the appropriate analysis for each of the question he has in mind.

Please explain why you choose such appropriate analysis and explain in detail on which data to be analyzed and how.