The collection of all possible outcomes of a random phenomenon is called

Sample Space

Explanation:

Sample Space, which is also known as sample description space or possibility space is the set of all possible outcomes or results of an experiment/random phenomenon.

An example of Sample Space is the tossing of a coin. When tossing a coin, two outcomes are possible -  head and tail. Therefore the sample space is given as  set {head, tail}, commonly written {H, T}.

Another example is in the throwing of a dice. When a single die is cast, there would be 6 outcomes, as a die has 6 faces. Therefore, the sample is given as

S = { 1, 2, 3, 4, 5, 6}.