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IB Maths AI 4.6 Notes

This page contains our IB Maths AI notes for 4.6. By reading each one of these notes, you will fully cover the content for IB Maths AI 'Probability distributions'.

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Discrete random variables

A random variable is a variable whose value depends on the outcome of a chance process. In this section, the focus is on discrete random variables, their probability distributions, expected value, the binomial distribution, and standardization of normal variables using zz-values.

A discrete random variable can take a finite or countable set of values. For example, if a fair die is rolled and XX is the score obtained, then XX can take the values 1,2,3,4,5,61,2,3,4,5,6.

A probability distribution lists all possible values of the random variable together with their probabilities.

For a valid probability distribution:

  • each probability must be between 00 and 11
  • the probabilities must add to 11

Check that the following probability distribution is valid.

xx1122334455
P(X=x)P(X=x)0.10.10.20.20.150.150.050.050.50.5

Check that it is valid: 0.1+0.2+0.15+0.05+0.5=10.1+0.2+0.15+0.05+0.5=1

So, the distribution is valid.

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