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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:

Re: Easy probability [#permalink]
15 Nov 2007, 14:26

1

This post received KUDOS

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

Re: Easy probability [#permalink]
21 Dec 2007, 14:39

1

This post received KUDOS

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:

Re: Easy probability [#permalink]
27 Sep 2009, 01:32

1

This post received KUDOS

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:

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.
_________________

Re: Easy probability [#permalink]
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.

Re: Easy probability [#permalink]
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: