Determine theProbability by sample

If S is a sample space and A is an event in the sample space, then the probability of A happening is:

P(A)=

Range of probability value is: 0 P(A) 1P(A) = 1 is called a certain eventP(A) = 0 is called an impossible event

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Example :

Look at the event of dice throwing.

The outcomes possibility are 1, 2, 3, 4, 5, or 6.

So the sample space is S= {1,2,3,4,5,6}

Suppose the outcomes of even spots dice is E={2,4,6}.

The number of set E is denoted by n(E),

so n(E)=3

We use the way as follow:

S= {1,2,3,4,5,6} , so n(S) = 6

E= {2,4,6} , so n(E)= 3

P(E)=2

1

6

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EXERCISE

there is a dice that will be tossed. Determine the probability of appearing:

a. 2

b. Numbers in a dice that less than 4

c. 7

d. 1, 2, 3, 4, 5, or 6

Expected frequency of an event is a probability

that is done in many times. If A is an event of

an experiment and this experiment is done n

times then the probability of event A in n

experiments is :

Expected frequency

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Example :

1. A coin which consists of the number side and the picture sidetossed 100 times. How many the probability of appearing number side?Answer : If the coin is tossed 1 time, the probability of appearing picture side is 1 / 2. Because the probability of appearing of picture side for 1 time tossed is 1 / 2, then for tossed 100 times, we will get:

501002

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nAPAF

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