its composed of social security and medicare, beside that it depends on the number of dependents you have.
social security and medicare is the same for anyone with a same income. but the federal tax depends on the number of dependents. most prolly, ur frens who make the same amout as you do,have stated they have more dependents so their tax is less, and may be u have stated and no dependents,hence u pay more in ur paycheck
but come jan,when u get ur w4, and file for ur taxes..then it is calculated ,and if you have paid more you get refunded......for the difference.
if ur making 32k -78, ud pay 25%..its marginal thought
anyways..if htey are taking too much ud most likely to get a refund,,or just go to the HR and add some dependnents..doesnt matter how many u add...but again, when u file tax in jan,,ad u dont have dependents..and if they have deducted l ess tax from ur paychekc..you might instead have to pay more in taxes...