1. Starter Find the probability that a person is ready for digital TV
Colmnar Bruntion poll was published about people’s readiness for digital TV
Are you ready for digital TV NZ
European
Other
TOTALS
Yes
4045
1673
5718 No
828
390
1218
4873
2063
6936
Find the probability that a person is ready for digital TV
Given that a person is ready for digital TV, find the prob that they are NZ European
Is being ‘NZ European’ and being ‘ready’ for digital TV independent of each other?
5718/6936
4045/5718 NO

2. Note 11: Probability Trees
Tree diagrams are useful to display possible ways of getting given results.
If events are connected by and probabilities are multiplied
If events are connected by or probabilities are added

3. Example:
A bag contains two white marbles and two black marbles. One marble after another is drawn (without replacement) until two black marbles have been drawn.
What is the probability that exactly three draws are required?

4. ✔ ✔
P(exactly 3 draws for 2 black marbles) = ⅓

5. Page 170
Exercise H