Do I need to have an EIN if I will hire a babysitter for a couple of months, will pay more than $1900, and will withhold taxes deduction from her? What should I deduct?

 If I want to withhold taxes from her payment, how much and what should I deduct? If I will not deduct taxes from her payment, do I need an EIN if the total payment per year is more than $2000? thanks