All employees, including part-time and temporary workers, are counted for purposes of determining whether an employer has a sufficient number of employees.
An employee is someone with whom the employer has an employment relationship. The existence of an employment relationship is most easily shown by a person's appearance on the employer's payroll, but this alone does not necessarily answer the question. Determining whether an employer has enough employees to be covered by these laws is, ultimately, a legal question. This subject is addressed in:
Independent contractors are not counted as employees. Determining whether an individual is, under the law, an independent contractor, also is a legal question that may not be as easy to answer as you might think. For more information on how to determine whether a person is an "employee" or an "independent contractor" visit The Difference Between Independent Contractors and Employees
If you are unsure whether your business is covered, or whether an individual who works for you is covered, you may wish to consult with an attorney.