## hockeychick23 one year ago Using the tree diagram, you just constructed and make a table showing the probability distribution of getting zero, one, or both questions right by guessing. (i attached the tree diagram)

1. hockeychick23

2. hockeychick23

@welshfella @kropot72

3. hockeychick23

I got: Probability of getting zero questions right by guessing: .5626(.75)= .42195 Probability of getting one question right by guessing: (0.75)(.1875)= .140625 (0.25)(.0625)= 0.015625 .140625+0.015625= .15625 but I'm not sure if i did it correctly, can someone check my answer please?

4. UnkleRhaukus

don't multiply

5. UnkleRhaukus

the number on the right most nodes are the total probabilities already

6. hockeychick23

oh ok so the probability of getting zero right is .5625, getting one right is .25+.1875=.4375 and getting both right would be .1875?

7. UnkleRhaukus

|dw:1433151671567:dw|

8. UnkleRhaukus

yes the probability of getting zero right is .5625,

9. UnkleRhaukus

the probability of getting 1 right is the sum of the two probability of the nodes in the tree that are exactly 1 right ansewer

10. hockeychick23

yea i got .25+.1875=.4375

11. UnkleRhaukus

ie P(1) = P(wr) + P(rw)

12. UnkleRhaukus

0.25 is the probability that the first question is right, but we want to add the probabilities that exactly one question is right

13. hockeychick23

oh sorry so its .1875+.0625= .25

14. UnkleRhaukus

nope

15. UnkleRhaukus

16. hockeychick23

.375

17. UnkleRhaukus

yes

18. hockeychick23

and then both right would be .1875

19. UnkleRhaukus

**error in diagram |dw:1433152335528:dw|

20. UnkleRhaukus

there is only one leaf on the tree that has both right answers P(rr) =

21. hockeychick23

yea that leaf says .0625

22. UnkleRhaukus

|dw:1433152413453:dw|

23. UnkleRhaukus

yes,

24. hockeychick23

i think i drew my diagram wrong when i constructed it

25. UnkleRhaukus

why do you say that? it seems right to me its multiple choice (four options) two questions

26. hockeychick23

oh i just flip flopped the wrong and right on the second leaf

27. UnkleRhaukus

ah yeah

28. UnkleRhaukus

if we add up all the probabilities P(0) = 0.5625 P(1) = 0.1875+0.1875 = 0.3750 P(2) = 0.0625 P(0)+P(1)+P(2) = 1

29. hockeychick23

oh awesome! so if i made it into a table like it was asking could i just draw it like this:

30. UnkleRhaukus

wcheck that last entry in the table again

31. hockeychick23

oh its not .1875? I thought that was what it was

32. hockeychick23

oh its .375

33. UnkleRhaukus

for both right: 1/4 * 1/4 =

34. UnkleRhaukus

nope 0.375 is for exactly 1 right

35. hockeychick23

36. hockeychick23

sorry i typed it incorrectly, this is the table

37. UnkleRhaukus

now to be sure check the sum all the probabilities .5625 + .375 + .0625 =

38. hockeychick23

.5625+.375+0.0625=1

39. UnkleRhaukus

Yay!

40. hockeychick23

:) thanks so much!!