Holt CA Course 1

8-2 Experimental Probability

SDAP3.2 Use data to estimate the probability of future events (e.g., batting averages or number of accidents per mile driven).Also covered: SDAP3.3

California Standards

Holt CA Course 1

8-2 Experimental Probability

Vocabulary

experimental probability

Holt CA Course 1

8-2 Experimental Probability

Experimental probability is one way of estimating the probability of an event. The experimental probability of an event is found by comparing the number of times the event occurs to the total number of trials when repeating an experiment many times. The more trials you have, the more accurate the estimate is likely to be.

Holt CA Course 1

8-2 Experimental Probability

Holt CA Course 1

8-2 Experimental Probability

During skating practice, Sasha landed 7 out of 12 jumps. What is the experimental probability that she will land her next jump? Write your answer as a ratio, as a decimal, and as a percent. Then explain why your answer is reasonable.

Additional Example 1: Sports Application

P(event) number of times an event occurstotal number of trials

Substitute data from the experiment.

712=

number of jumps landednumber of jumps attemptedP(jumps landed)

≈ 0.583 ≈ 58.3% Write as a decimal and as a percent.

Holt CA Course 1

8-2 Experimental ProbabilityAdditional Example 1 Continued

The experimental probability that Sasha will land her

next jump is or 0.583, or 58.3%.7

12

Sasha landed about half, or 50%, of the 12 jumps, so an answer of 58.3% is reasonable.

During skating practice, Sasha landed 7 out of 12 jumps. What is the experimental probability that she will land her next jump? Write your answer as a ratio, as a decimal, and as a percent. Then explain why your answer is reasonable.

Holt CA Course 1

8-2 Experimental Probability

“P(event)” represents the probability that an event will occur. For example, the probability of a flipped coin landing heads up could be written as “P(heads).”

Writing Math

Holt CA Course 1

8-2 Experimental ProbabilityCheck It Out! Example 1

During basketball practice, Martha made 9 out of 10 free throws. What is the experimental probability that she will make her next attempt? Write your answer as a ratio, as a decimal, and as a percent. Then explain why your answer is reasonable.

P(event) number of times an event occurstotal number of trials

Substitute data from the experiment and write as a percent.

910=

P(free throws made) number of free throws madenumber of free throws attempted

= 0.9 = 90% Write as a decimal and as a percent.

Holt CA Course 1

8-2 Experimental ProbabilityCheck It Out! Example 1 Continued

The experimental probability that Martha will make the

next free throw is , or 0.9, or 90%.

910

Martha made almost all, or 100%, of the 10 free throws, so an answer of 90% is reasonable.

During basketball practice, Martha made 9 out of 10 free throws. What is the experimental probability that she will make her next attempt? Write your answer as a ratio, as a decimal, and as a percent. Then explain why your answer is reasonable.

Holt CA Course 1

8-2 Experimental Probability

Students have checked out 55 books from the library. Of these, 32 books are fiction.

Additional Example 2: Application

A. What is the experimental probability that the next book checked out will be fiction?

P(fiction) number of fiction books checked outtotal number of books checked out

= 3255

The experimental probability that the next book

checked out will be fiction is 32 55.

Substitute data.

Holt CA Course 1

8-2 Experimental Probability

B. What is the experimental probability that

Additional Example 2: Application

the next book checked out will be nonfiction?

P(fiction) + P(nonfiction) = 1

+ P(nonfiction) = 1

The experimental probability that the next book checkedout will be nonfiction is approximately

23 55.

Substitute.3255

Use the complement.

Subtract from both sides.

3255

P(nonfiction) = 2355

3255–=– 32

55

Students have checked out 55 books from the library. Of these, 32 books are fiction.

Holt CA Course 1

8-2 Experimental ProbabilityCheck It Out! Example 2

Students have a fruit choice of either an apple or a pear. So far 18 of 47 students have selected pears.

A. What is the experimental probability that the next fruit selected will be a pear?

= 1847

The experimental probability that the next fruit

selected will be a pear is 18 47 .

Substitute data.

P(pear) number of pears selectedtotal number of fruit selected

Holt CA Course 1

8-2 Experimental ProbabilityCheck It Out! Example 2

P(pear) + P(apple) = 1

+ P(apple) = 1

The experimental probability that the next fruit selected will be an apple is 29

47 .

Substitute.1847

Use the complement.

Subtract from both sides.

1847

P(apple) = 2947

1847

–=– 1847

B. What is the experimental probability that next fruit selected will be an apple?

Students have a fruit choice of either an apple or a pear. So far 18 of 47 students have selected pears.