Final answer:
The possible values for the random variable 'number of slips marked '1'' when two slips are selected without replacement from a box containing slips marked '1', '2', '3', and '4' are 0, 1, or 2.
Step-by-step explanation:
The random variable in this question is the number of slips marked '1' that are selected from the box without replacement. Since there are four slips in the box marked '1', the possible values for this random variable are 0, 1, or 2. This is because if no slips marked '1' are selected, the value is 0. If one slip marked '1' is selected, the value is 1. If two slips marked '1' are selected, the value is 2.