Probability and Simple Experiments

Probability and Simple Experiments

Probability describes how likely an event is. An impossible event has probability 0, a certain event has probability 1, and equally likely outcomes can be counted as favourable outcomes over total outcomes. Experimental probability comes from real trials, so it can differ from the theoretical value, especially with a small number of trials.

Worked example

A fair coin has two equally likely outcomes. Probability of heads is $1/2$. In 10 tosses, you may not get exactly 5 heads; more trials usually make the experimental result closer to $1/2$.

Exam method

1. List equally likely outcomes. 2. Count favourable outcomes and total outcomes. 3. Write a fraction and decide whether the result is reasonable between 0 and 1.