2. Definition
•Probability is the measure of how likely
something will occur.
•It is the ratio of desired outcomes to total
outcomes.
•Probabilities of all outcomes sums to 1.
3. Example
•If I roll a number cube ,there are six total
possibilities (.1,2,3,4,5,6)
•Each possibility only has one outcome, so each has
a PROBABILITY of ½.
•For instance ,the probability I roll a 2 is ½, since
there is only a single 2 on the number cube.
4. Practice
IF I FLIP A COIN , WHAT IS THE PROBABILITY I GET HEADS?
ANS :_______________
WHAT IS THE PROBABILITY TO GET TAILS?
ANS :_______________
HOW MANY POSSIBILITIES THERE ARE IN THIS QUESTION?
ANS :_____________________________________________________
P(HEADS) =½
.
P(TAILS) =½.
IF YOU ADD THESE TWO UP ½ + ½ , YOU WILL GET 1.
5. Two or more events
•If there are two or more events, you need to consider if it is
happening at the same time or one after the other.
6. more events
•If the two events are happening at the same
time, you need to multiply the two probabilities
together.
•Usually, the questions use the word “and ”when
describing the outcomes.
7. Experimental probability
•An experimental probability is one that happens
as the result of an experiment.
•The probabilities we have done far are “theoretical
probabilities ”tnemirepxe on saw ereht esuaceb ,.
8. Real life examples
games and competitions. A baseball coach evaluates a player's batting average
when placing him in the lineup. For example, a player with a 200 batting average
means he's gotten a base hit two out of every 10 at bats. A player with a 400
batting average is even more likely to get a hit -- four base hits out of every 10 at
bats. Or, if a high-school football kicker makes nine out of 15 field goal attempts
from over 40 yards during the season, he has a 60 percent chance of scoring on
his next field goal attempt from that distance. The equation is:
9/15=0.60 or 60 percent
