## aussy123 2 years ago Matching probability question help! Medal Rewarded!!

1. aussy123

In a group of 100 persons, 85 had Rh positive blood (Rh factor present), 45 had Type O blood, and 38 had both type O and Rh positive blood. If one person had been selected at random from the group, what would the probability be: 1. that his blood type was Type O and Rh+? A. 3 /20 2. that his blood type was not O? B. 17/20 3. that his blood type was Rh-? C . 93/100 4. that his blood type was Type O and Rh-? D. 11/20 5. that his blood type was Rh+? E. 7/100 6. that his blood type was not Type O or else was Rh+? F. 19/50

2. amistre64

a venn might be usefull

3. aussy123

whats that

4. amistre64

its a diagraham that defines sets with circles

5. aussy123

Oh where can I find it

6. amistre64

|dw:1366391420781:dw|

7. aussy123

Oh

8. amistre64

|dw:1366391462898:dw|

9. amistre64

if we add the 3 sections we get: 85+45-38 = 92 so there must be 8 people in the setup that had neither Rh or O

10. aussy123

ok..Im following

11. amistre64

|dw:1366391683621:dw|

12. amistre64

this helps us define the numbers involved and the combinations that they ask for

13. amistre64

1. that his blood type was Type O and Rh+? A. 38 /100 2. that his blood type was not O? B. (100 - 45)/100 3. that his blood type was Rh-? (not RH) C. (100 - 85)/100 4. that his blood type was Type O and notRh? D. 45/100 * C 5. that his blood type was Rh+? E. 85/100 6. that his blood type was not Type O or else was Rh+? F. B + E

14. aussy123

One question just so I know Im reading the diagram right. Is Rh. n. O , Rh.NOT.O?

15. amistre64

there are 2 symbols in set theory; "n" and "u" n = AND u = OR

16. aussy123

ohh I see, makes sense.

17. amistre64

"and" defines the intersection (commonality) of sets

18. amistre64

im thinking F might be off

19. aussy123

so #1 from what I see is A #2 is D

20. amistre64

|dw:1366392293192:dw| notO or Rh is: (100-7)/100 i had a repetition in there

21. aussy123

Ok now Im a bit confused.

22. amistre64

notO includes the areas: 47, 8 Rh includes the areas: 47, 38 if we add these together to find the probability of notO or Rh, im doubling an area.

23. aussy123

oh

24. amistre64

4. that his blood type was Type O and notRh? this one might be off as well |dw:1366392674723:dw| the commonality of O "and" notRH is spose to be 7/100

25. amistre64

other than that, i think its sound :)

26. aussy123

so was I right about #1 and #2

27. amistre64

yes, it might help to rewrite the options in 100 format A. 15/100 B. 85/100 C . 93/100 D. 55/100 E. 7/100 F. 38/100 that should be more intuitive

28. aussy123

okay Thanks

29. amistre64

good luck :)

30. CarlosGP

@aussy123, @amistre64 has been quicker than me. I was preparing these tables for you. In the first table you have the given data in green and the calculated data in yellow. The other sisx tables correspond to each question of the problem where I have shaded in green the data to consider. Though late, I hope it helps

31. aussy123

Oh Cool thats very helpful! Thanks to the both of you!!

32. amistre64

nice tables, im not sure if i could process those in that manner ...

33. CarlosGP

@amistre64, thanks. They are known as contingency tables in Statistics