04 "Or" Probabilities for Statistics

P(A or B) =

• P(A) + P(B) - P(A and B)

• P(A) + P(B)

• P(A)∙P(B|A)

• P(A)∙P(B)

When does P(A or B) = P(A) + P(B) ?

• Always

• Never

• When A and B are disjoint in relation

• When A and B are overlapping in relation

If two Events A and B are disjoint in relation, which of the following are necessarily true?

• P(A or B) = P(A) + P(B)

• P(A and B) = 0

• P(A and B) = 1

• P(A and B) = P(A)∙P(B)

Two Events are disjoint in relation when they have...

• No outcomes in common

• Exactly one outcome in common

• At least one outcome in common

• All outcomes in common

Two Events are overlapping in relation when they have...

• No outcomes in common

• Exactly one outcome in common

• At least one outcome in common

• All outcomes in common

In the Addition Rule, why do we subtract P(A and B)?

• Because some outcomes were counted twice

• Because the outcomes in the middle shouldn't count

• Because "or" in Statistics means "exclusive or."

• Because the common outcomes have a lower weight

If a person is selected at random from the people described by the table shown, what is the probability they will be a boy or have brown hair?

• 70%

• 95%

• 25%

• 68.5%

If you roll a fair six-sided die, what is the probability of getting an odd number or a prime number?

• 2/3

• 1/3

• 1/2

• 5/6

A bag contains 9 green marbles, 5 yellow marbles and 6 red marbles. You select one marble. What is the probability of selecting a green or red marble?

• 8/15

• 6/11

• 3/4

• 2/3

Consider the Venn Diagram shown. If a species is selected at random from this diagram, what is the probability it can swim or breathe air?

• 2/5

• 14/15

• 1/4

• 2/3