Schéma relationnel :

1. Employee (EmployeeID, FirstName, LastName, Email, Phone, HireDate, Salary, #DepartmentID)
2. Department (DepartmentID, DepartmentName, #ManagerID)
3. Project (ProjectID, ProjectName, StartDate, EndDate, Budget)
4. Employee_Project (#EmployeeID, #ProjectID, Role, AssignmentDate)

Explication des relations :

• Employee (EmployeeID) est la clé primaire.
• Department (DepartmentID) est la clé primaire.
• Project (ProjectID) est la clé primaire.
• Employee_Project (#EmployeeID, #ProjectID) est une clé primaire composite (relation plusieurs-à-plusieurs entre Employee et Project).
• Employee(#DepartmentID) → Department(DepartmentID) : Un employé appartient à un département.
• Department(#ManagerID) → Employee(EmployeeID) : Un manager est un employé.
• Employee_Project(#EmployeeID) → Employee(EmployeeID)
• Employee_Project(#ProjectID) → Project(ProjectID)

QUESTION

Relational Schema:

Employee (EmployeeID, FirstName, LastName, Email, Phone, HireDate, Salary, #DepartmentID)

Explanation of Relationships:

• Employee (EmployeeID) is the primary key.
• Department (DepartmentID) is the primary key.
• Project (ProjectID) is the primary key.
• Employee_Project (#EmployeeID, #ProjectID) is a composite primary key (many-to-many relationship between Employee and Project).
• Employee(#DepartmentID) REFERENCES Department(DepartmentID): An employee belongs to a department.
• Department(#ManagerID) REFERENCES Employee(EmployeeID): A manager is an employee.
• Employee_Project(#EmployeeID) REFERENCES Employee(EmployeeID)
• Employee_Project(#ProjectID) REFERENCES Project(ProjectID)

QUESTION

A 1992 Roper poll found that 22% of Americans say that the Holocaust may not have happened. The actual question asked in the poll was:

A questionnaire on a table at a shopping centre was completed by 100 shoppers.

The results were used to claim that the average amount of money spent by Australians increased from the previous year.

Which one of the following biases makes this survey questionable?

To assess the opinion of students about campus safety at your campus of Monash University, a reporter for the student newspaper interviews 15 students she meets walking on your campus late at night who are willing to give their opinion.

Olivia wants to learn a foreign language. To get an idea of how satisfied other students were after taking a foreign language course, she decides to take a random sample of 20 students.

A random sample of 800 airline passengers is wanted from 100 particular flights leaving Sydney Airport. Assume there are 200 passengers aboard each flight.

A numbered list of all 100 x 200 = 20,000 passengers on these flights was obtained. One passenger was drawn from each set of 20,000/800 = 25 passengers. Randomly choose among the first 25 passengers on the list to start, and then choose every 25th passenger until 800 passengers were obtained.

What type of sampling technique is this?

Which of the following statements best describes the main difference between a survey and a census?

Taxpayers in a population are listed in order of increasing income, with people with the lowest incomes listed first. A sample is selected by randomly choosing one of the first 1000 names, then choosing every 1000^th name from that point forward.

What is the type of sampling design in this approach?

Each month the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don't return the form. In one month, responses were obtained from 240,000 of the households contacted.