r/HomeworkHelp • u/pumkinspicedeodorant University/College Student • 1d ago

Additional Mathematics—Pending OP Reply [College Statistics: Multiplying Probabilities] What am I doing wrong here?

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The directions say I don’t have to simplify my fractions, but it won’t be counted against me if I do. The third pic is the data table the question is based on.

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u/GammaRayBurst25 1d ago

The condition "1st did not feel worse" means 1 person who did not feel worse was removed from the pool. Hence, the numerator and the denominator should both decrease by 1. The same logic applies to the condition that both the 1st and the 2nd did not feel worse, except now 2 people are removed from the pool.

P.S. take a screenshot next time.

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u/pumkinspicedeodorant University/College Student 1d ago

I’ve solved it recently. I knew the fraction was 135/203. I thought I needed to multiply it by the previous fraction already. But that wasn’t until the next step.

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u/Alkalannar 1d ago

P(1st did not feel worse) = 136/204

P(2nd did not feel worse | 1st did not feel worse) = 135/203

P(3rd did not feel worse | 1st and 2nd didn't feel worse) = 134/202.

Or this is the same as Choosing 3 people out of the Not-Worse category divided by Choosing 3 people out of the whole: (136 C 3)/(204 C 3).

[Or ordering them: (136 P 3)/(204 P 3). This is what your problem is doing by choosing them in order.]

Either way you get (136*135*134)/(204*203*202) as your answer.