Module 1-3 |
Probability: is a number between 0
and 1 (fraction) that tells how likely it is that an event will take
place. The closer to 1 the more likely it is that the event will occur. A probability of one, means that the event will always occur. A probability of zero, means that the event will never occur. Outcomes are equally likely if they have the same chance of occurring. Event: What outcome you are testing. Outcome: What actually happens. Example, in a bag of colored marbles, the event would be the likelihood of picking a particular color. If there were 3 red, 4 blue and 3 green marbles, what is the likelihood of picking a red marble? Experimental probability: When you actually do the event (toss a coin) and count up the actual outcomes. Example: I toss a coin 50 times and 29 out of 50 land on heads. Theoretical probability: You don’t actually do the experiment. Count up how many possible positive outcomes there can be over how many actual outcomes there are. Example 1: On a fair coin there is
one head, and one tail. That means there is a total of 2 possible
outcomes. The probability of getting a head is 1 out of 2 or
. Example 3: If there were 3 red, 4
blue and 3 green marbles, what is the P(red or blue)? Notice how we
wrote this probability question. It means what is the probability of
picking a red or a blue marble. Since there are 3 red marbles and 4 blue
marbles there are 7 possible positive outcomes out of 10 total possible
outcomes so the P(red or blue) is
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