/sci/ - Science & Math » Thread #12415052

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How do I solve this? My exam is in one hour please help!

Anonymous Thu 03 Dec 15:04:46 2020 No.12415052 View Reply Original Report

Quoted By: >>12415094 >>12415105

Approximately 10% of people are left-handed. If two people are selected at random, what is the probability of the following events?
a. Both are right-handed.
b. Both are left-handed.
c. One is right-handed and the other is left-handed.
d. At least one is right-handed.
please explain how its done, my exam is in one hour and am stuck on this one

Anonymous

Anonymous Thu 03 Dec 2020 15:06:14 No.12415056 Report

Quoted By:

Draw a probability tree.

Anonymous

Anonymous Thu 03 Dec 2020 15:10:40 No.12415066 Report

Quoted By:

but it says the answer is 0.81 if I Draw a probability tree wouldn't the answer be 1/4=.25??

Anonymous

Anonymous Thu 03 Dec 2020 15:11:43 No.12415070 Report

Quoted By:

this one
a. both are right-handed = 0.81

Anonymous

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Anonymous Thu 03 Dec 2020 15:17:58 No.12415089 Report

Quoted By:

This is just basic probability anon. Did you not pay attention to your lectures.
think of 1 as 100%
P of LH is 1/10
so P of RH is 1 - P(LH) = 9/10
a. is P(RH) * P(RH)
b. you should be able to solve this now
c. Just visualize a tree structure and all its possibilities to meet this statement. P(RH) * P(LH) + P(LH) * P(RH)
d. you should be able to solve this now

Anonymous

Anonymous Thu 03 Dec 2020 15:18:38 No.12415094 Report

Quoted By:

>>12415052
p=probability of being left handed

a) (1-p)(1-p) = 0.81
b) p*p=0.01
c) p(1-p) + (1-p)p = 0.18
d) 1 - (p*p) = 0.99

Anonymous

Anonymous Thu 03 Dec 2020 15:22:26 No.12415105 Report

Quoted By:

>>12415052
Just think of flipping a biased coin twice. Heads means right handed (p(H) = .9) Tails means left handed (p(T)=.1)
Then just enumerate the possible outcomes:

p(H,H) = .9*.9 = .81
p(T,T) = .1*.1 = .001
p(H,T) = .9*.1 = .09
p(T,H) = .1*.9 = .09

a and b are immediate from here. For c, you add the last two outcomes. For d you do 1 - p(TT)

Anonymous

Anonymous Thu 03 Dec 2020 15:28:44 No.12415128 Report

Quoted By:

I feel so stupid thanks everyone one for the help. I can solve it now!

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