# proability

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• Created by: shona
• Created on: 27-12-12 12:31

## probability

RELATIVE FREQUENCY

• the probability of an event can be found by carrying out many trials and calculating the relative frequency or experimental probability
• to calculate the relative frequency divide the number of times the event occurred during the experiment by the total number of trials done in the experiment
• ther higher the number of trials carried out the nearer the experimental probability will be to the true probabilty

MUTUALLY EXCLUSIVE AND EXHAUSTIVE EVENTS

• when the out come of event A can never happen the same time as event B then the events are said to be mutually exclusive
• when the probabilty of mutually exclusive events add up to 1 they are called exhaustive events
• if there is an event A the complementary event of A is event A not happening
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## probability

EXPECTATIONS:

• when the probability of an event is known you can predict how namy times the event is likely to happen in the given number of trials
• this is the expectation this is not what is going to happed
• the expected number is calculated as: expected number= P(event) x total trials

TWO WAY TABLES:

• a two way tables is a table that links two variables
• one of the variables s shown by the rows of the tables
• one of the variables id shown by the colomns of the tables

• to work out the probability of two mutually exclusive events happening add the probabilities of all the seperate events: P(A OR B)= P(A) + P(B)

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