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Easy probability

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Easy probability [#permalink] New post 15 Nov 2007, 14:15
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A
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Difficulty:

  5% (low)

Question Stats:

76% (01:55) correct 23% (00:47) wrong based on 51 sessions
GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031
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Re: Easy probability [#permalink] New post 15 Nov 2007, 14:26
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GMAT TIGER wrote:
GMATT73 wrote:
GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031


= 0.5^5
= close to 0.000


I make it D - 0.5 x 0.5 x 0.5 x 0.5 x 0.5 - which is 1/32 or closest to 0.31
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 [#permalink] New post 15 Nov 2007, 14:26
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D .031

probability of guessing it right = .5
So probability of guessing all 5 right = (.5)*(.5)*(.5)*(.5)*(.5) = .031
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CEO
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 [#permalink] New post 21 Dec 2007, 06:46
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pretty straightforward question.

binomial prob
p(hit) = p(miss) = .5 = 1/2

(1/2)^multiplier
(1/2)^5 = 1/32 = .03xxx
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Re: Easy probability [#permalink] New post 21 Dec 2007, 14:39
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GMATT73 wrote:
GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031


Whoops misread somethin.

1/2^5 ---> 1/32 So D.
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Re: Easy probability [#permalink] New post 27 Sep 2009, 01:32
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GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031


Soln: (1/2) ^ 5 = 1/32 = .031
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CEO
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Re: Easy probability [#permalink] New post 30 Mar 2010, 06:18
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bnagdev282 wrote:
whats wrong in this

P(missess none)
= 1-prob(missess all)
= 1- (1/32)
= 31/32

pls explain thks


You should have use this if they had asked he atleast got 1 right
then that P = 1-( P( no right) )

here it is asked he doesnt miss all
you have skipped the case when he missed 1,2,3,4 questions wrong.
p(1) = 1/2
p2 = 1/4
p3 = 1/8
p4 = 1/16 now subtract p1+p2+p3+p4 = 0.9375
from 31/32=0.96875
you will get p =0.03125
Hence D..... Do not down the cases you didnt considered .
Hope this helps.
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Re: Easy probability [#permalink] New post 15 Nov 2007, 14:35
alrussell wrote:
GMAT TIGER wrote:
GMATT73 wrote:
GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031


= 0.5^5
= close to 0.000


I make it D - 0.5 x 0.5 x 0.5 x 0.5 x 0.5 - which is 1/32 or closest to 0.31


yup yup agree with D. 0.031.

thought 0.5 to the power 5 would result in negligible value close to 0.
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 [#permalink] New post 15 Nov 2007, 14:38
Answer is naturally D. Guess I had better study instead!
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Re: Easy probability [#permalink] New post 21 Dec 2007, 19:00
GMATT73 wrote:
GMATT randomly guesses the answers to a five-question true/false section on his stats final. If there is a 0.50 probability of making the correct choice on each question, then the probability that GMATT misses no questions is:

A) 0.000
B) 0.200
C) 0.500
D) 0.031


=0.5*0.5*0.5*0.5*0.5
=0.03125

Answer is D
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Re: Easy probability [#permalink] New post 24 Jul 2009, 18:15
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Re: Easy probability [#permalink] New post 04 Mar 2010, 03:47
It´s great to work through this questions with all of you guys! It feels almost like a group work :lol:
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Re: Easy probability [#permalink] New post 30 Mar 2010, 02:48
whats wrong in this

P(missess none)
= 1-prob(missess all)
= 1- (1/32)
= 31/32

pls explain thks
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Re: Easy probability [#permalink] New post 18 Jun 2011, 06:03
0.5^5 = 1/32 = 0.031
ans D
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Re: Easy probability [#permalink] New post 28 Nov 2011, 08:08
Pro = (1/2)^5 = .031
Re: Easy probability   [#permalink] 28 Nov 2011, 08:08
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