Twenty Children Are Given Several Sessions of Guided Play with Liquids

Multiple Choice

Twenty children are given several sessions of guided play with liquids and containers, while another 20 children serve as controls. Each child is tested on a liquid conservation task and it is found that 15 of the guided play children show conservation on the task whereas only 8 of the control children do so.
-5) The expected frequency for control children conserving is:

A) 12.5
B) 8
C) 11.5
D) 15