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Stats problem. who is bored

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invader7
Posts: 5756 - Karma: 49
Over time, a student analyzes her ability to guess correctly after narrowing down mutiple choice answers in a 5-selection question (choices a through e). She discovers that if she narrows her answer set to 2 or 3 choices, her probability the right answer is 0.8, but if she still has 4 or 5 choices 70% of the time, What is the probability that she will answer a question correctly any time she must guess? Draw the tree diagram & justify your answer.
Jan 3 2010 6:37PM
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Totes_Magotes
Posts: 2259 - Karma: 870
7
Jan 3 2010 6:48PM
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Jib-Ninja
Posts: 2819 - Karma: 20
7
Jan 3 2010 6:59PM
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Flo_Rida_2016
Posts: 2804 - Karma: -5
what? retype the question, work on your english.

I think youre saying if she has 2 or 3 choices her proabblity of getting it right is .8?

If she has 4 or 5 her probability is .7? What are the frequencies for having 2/3 or 4/5
Jan 3 2010 7:00PM
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invader7
Posts: 5756 - Karma: 49
thats why im having trouble with it. that is exactly how it is typed on my paper
Jan 3 2010 7:26PM
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purps
Posts: 468 - Karma: 30
.38 or 38%
Jan 3 2010 7:30PM
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invader7
Posts: 5756 - Karma: 49

Over time, a student analyzes her ability to guess correctly after narrowing down mutiple choice answers in a 5-selection question (choices a through e). She discovers that if she narrows her answer set to 2 or 3 choices, her probability the right answer is 0.8, but if she still has 4 or 5 choices her probability of choosing the right answer quickly decreases rapidly to .1 assuming that in general she can narrow her choices to  2 or 3 70% of the time, What is the probability that she will answer a question correctly any time she must guess? Draw the tree diagram & justify your answer.

correction. my bad and i was wrong

Jan 3 2010 7:39PM
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purps
Posts: 468 - Karma: 30

oooh ok

then its .31 i reckon 

Jan 3 2010 7:49PM
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invader7
Posts: 5756 - Karma: 49
bump
Jan 3 2010 9:22PM
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invader7
Posts: 5756 - Karma: 49
hump
Jan 3 2010 10:50PM
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FrenchToastMafia
Posts: 2195 - Karma: 452
fuck no clue, my high school stats teacher didnt teach me enought
Jan 3 2010 11:39PM
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Omega2227
Posts: 225 - Karma: 11
Haven't taken stat but what I know from tree diagrams should be something like 59%
you have the original question as your starter point, first brach is eitehr 70% or 30% that she can narrow down the question,

Then from there, if she narrows it down to 2 or 3 and guesses, she has an 80% chance, so .7 x .8 = .56
AND
if she can't narrow it down and guesses, she has a 10% chance of getting it right, so .3 x .1 = .03

therefore:
.56 + .03 = .59 = 59%

Hope this makes sense / helps
Jan 4 2010 12:02AM
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invader7
Posts: 5756 - Karma: 49
makes sense to me, and is better than the answer i had. thanks man and plus karma. and if anyone else has a better attempt feel free to still post.
Jan 4 2010 12:13AM
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superpoluha
Posts: 1986 - Karma: 10
newschoolers=/= homewoork hotline/homework help
Jan 4 2010 12:15AM
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*DrewT*
Posts: 7768 - Karma: 480

you think this is a bad question?  This is word for word a question from one of my stats tests last semester

The random variable X= number of pieces of Reese.

a. 9

b. 1

c. 8

d. 10

e. none of the above

Jan 4 2010 12:29AM
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AdolfShitler
Posts: 1618 - Karma: 32
Click for larger image
Jan 4 2010 12:54AM
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purps
Posts: 468 - Karma: 30
oh yeah, my bad. this is right. i mixed up the numbers thinking that the 70% one was for her not narrowing down her answers instead of actually narrowing down her answers. my mistake, thats what happens when i do it in my head i guess
Jan 4 2010 5:29PM
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purps
Posts: 468 - Karma: 30
sorry bout the double post but turns out i mixed the original problem and the second one
Jan 4 2010 5:30PM
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