A recent study investigates the determinants of employees' satisfaction. The hypothesis tests to what extent satisfaction is linked to: the educational level of employees within firms; the employees' tenure within the same firm; the annual leave days of the employees; number of employees' promotions within the same company. Data is collected from 1,234 UK firms.

Their dataset contains the following variables:

• The dependent variable is the average level of work satisfaction in the firm that can range between 1 and 10.
• Employee's educational level (i.e., the average years of education of the firm's employees on a scale from 0 to 10)
• Employee's tenure within firm (i.e., the average years of tenure of the firm's employees on a scale from 0 to 10)
• Number of annual leave days per employee.
• Number of employees' promotions.

As part of the research the following linear regression has been produced (Table 1).