Statistics Normal Distribution Question

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Madman11
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Hi, I was just doing this question and It’s not that bad, but I don’t understand the 2 lines I’ve marked. I know how to do the Maths, but I don’t understand why, after you’ve worked out what Z is (0.9479), you then switch that for 1.625. I left it as 0.9479 while doing everything else so the end answer I got was slightly off - 646. Anyone know why you switch out that number ?
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Madman11
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That’s the question if anyone was wondering - part B.
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boulderingislife
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(Original post by Madman11)
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Hi, I was just doing this question and It’s not that bad, but I don’t understand the 2 lines I’ve marked. I know how to do the Maths, but I don’t understand why, after you’ve worked out what Z is (0.9479), you then switch that for 1.625. I left it as 0.9479 while doing everything else so the end answer I got was slightly off - 646. Anyone know why you switch out that number ?
You have to use the phi table conversions. 0.9479 is a probability. You need to convert this to a phi number to do the maths. Look for an example in your textbook and you should see they convert it to a phi number in every case.
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Madman11
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Ah yeah I get that, but In this instance, we don’t know the mean or standard deviation, all we know is that they are in some form of P, so how would I go about doing that ?
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Madman11
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Ohhhhh never mind, u literally just use inverse normal ... how could I forget that lmaooo
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