Basic Terms of Probability

Objectives

• Determine the probability of a given event .

• Determine the odds of a given event.

• Use a Punnet square to determine probability.

Vocabulary

• experiment • sample space - the set S of all

possible outcomes of an experiment• event – any subset E of the sample

space S• probability – success divided by total• odds – success to failures

Formulas

)()(

)(SnEn

Ep

)(:)()( EnEnEo

A jar on your desk contains twelve black, eight red, ten yellow, and five green jellybeans.  You pick a jellybean without looking.

What is the probability that the jellybean is green?

A jar on your desk contains twelve black, eight red, ten yellow, and five green jellybeans.  You pick a jellybean without looking.

What is the probability that the jellybean is not yellow?

A jar on your desk contains twelve black, eight red, ten yellow, and five green jellybeans.  You pick a jellybean without looking.

What are the odds in favor of picking a black jellybean?

A card is drawn from a well-shuffled deck of 52 cards.

What is the probability that the card is a heart?

A card is drawn from a well-shuffled deck of 52 cards.

What are the odds of drawing a heart?

A card is drawn from a well-shuffled deck of 52 cards.

What is the probability that the card is below a 9 (ace high)?

A card is drawn from a well-shuffled deck of 52 cards.

What are the odds of a card below a 9 (ace high)?

A family has three children.  Using b to stand for boy and g to stand for girl, and using ordered triples such as(bbg) give:

the sample space

A family has three children.  Using b to stand for boy and g to stand for girl, and using ordered triples such as(b, b, g) give:

the event E that the family has exactly two daughters

A family has three children.  Using b to stand for boy and g to stand for girl, and using ordered triples such as(b, b, g) give:

the event F that the family has at least two daughters

A family has three children.  Using b to stand for boy and g to stand for girl, and using ordered triples such as(b, b, g) give:

the event G that the family has three daughters

Vocabulary

• dominant • recessive • Punnett square • codominant

Mendel found that snapdragons have no color dominance; a snapdragon with one red gene and one white gene will have pink flowers.  If a pure-red snapdragon is crossed with a pure-white snapdragon, find the probability of the following. • a red offspring

• a white offspring

• a pink offspring

If carrier-detection tests show that two prospective parents have sickle cell trait (and are therefore carriers), find the probability of each of the following • their child would have sickle cell

anemia.

• their child would have sickle cell trait.

• their child would be healthy (free of symptoms).

Tay-Sachs disease is a recessive disease. If carrier-detection tests show that one prospective parent is a carrier of Tay-Sachs and the other has no Tay-Sachs gene, find the probability of each of the following. • their child would have the disease.

• their child would be a carrier.

• their child would be healthy (free of symptoms)