4.1.3. Formulae Summary

Try these first

1. 1.

   What is the conditional probability formula?

   Hint

   Remember it involves the joint probability divided by the probability of the condition.

2. 2.

   Are two events independent if P(A|B) = P(A)?

   Hint

   Consider if the occurrence of one affects the other.

3. 3.

   What is the correct formula for conditional probability?

   • P(A) = P(A|B) * P(B)
   • P(A|B) = P(A ∩ B) / P(B)
   • P(B|A) = P(B) / P(A)

   Hint

   Look for the formula that includes both events A and B.

4. 4.

   True or False: If two events are independent, P(A|B) = P(A).

   • True
   • False

   Hint

   Consider what independence means in probability terms.

5. 5.

   In a deck of cards, what is the probability of drawing a red card given that an ace has been drawn?

   Hint

   Consider how many cards are left after one draw.

6. 6.

   A bag contains 3 red and 2 blue marbles. If one is drawn and is known to be red, what is the probability of drawing a second red marble?

   Hint

   Think about how many red marbles are left and total marbles remaining.