Which of the following is not correct regarding administration of cardiopulmonary resuscitation (CPR)?
1) CPR should be performed on a hard surface.
2) CPR should be performed with a compression-to-ventilation ratio of 30:2.
3) CPR should be performed with a compression depth of at least 5 centimeters.
4) CPR should be performed with a compression rate of at least 100 compressions per minute.