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Mathematics for science and technology
Mathematics for science and technology

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4 Ways of expressing probability

According to Equation 1, probability is defined as a fraction. However a fraction such as one divided by four may also be expressed as a decimal number or as a percentage:

equation sequence one divided by four equals 0.25 equals 25 percent

The following statements:

  • the probability of event A is one divided by four,
  • the probability of A occurring is 0.25,
  • there is a 25% probability of the outcome being A,

are therefore all equivalent.

In addition, particularly in spoken language, it is common to say,

  • there is a 1 in 4 probability of the outcome being A,

and that too is equivalent to the other three statements.

For the rest of this week probabilities will usually be expressed as fractions.

Now it is time to move on to probabilities that are related to more than one process.