Independent Vs Dependent Probability:
What’s the difference?
A bag contains 9 red marbles and 3 green marbles. What is the
probability of selecting a red marble on the first draw and a green marble
on the second draw if…
1) The first marble is replaced.
2) The first marble is not replaced.
Dependent Probability
• The probability of a second event depends on the outcome of the first
event.
• Usually the words “without replacement” are involved.
Socks in my dryer:
Pull 1 sock at a time…
1) P(green then blue)
2) P(red pair)
3) P(removing all greens)
4) P(hearts and spade)
5) P(hearts and 5)
6) P(Ace then red)
7) P(Face card and 6)
8) P(red or 5)
9) P(Face and Red)
Last example…
A school survey found that 9 out of 10 students like pizza. If three
students are chosen at random, what is the probability that all three
students like pizza?