In probability theory, an experiment is a pocedure that can be repeated any number of times and has a definite set of possible outcomes, known as the sample space. There is a probability associated with each outcome.
a. Tossing a coin is an experiment because we have 2 possible outcomes head and tail and a sample apce consisting of head and tail.
b. Choosing a specific coloured ball from a collection of different coloured balls . This is an experiment with only 1 outcome since we are selecting a specific coloured ball.
c. Buying a pen is not an experiment as the set of outcomes is not clearly defined.