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# Confused, Can you help ?

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Apr 5, 2019

#1
+1534
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While your composing that one I would like to post this one as well. I am confused on this one too

Apr 5, 2019
#2
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We want to find the  z score in the table that corresponds to  .20   [ or....at least as close as possible]

Looking at the table here : http://www.z-table.com/    ....  we find that this corresponds to a z score of ≈ -.84

So....the 'formula" for our  z score is

[ mass we are trying to find - mean ]

________________________________  =  -.84              fill in what we know

std dev

[ mass we are trying to find  - 55 ]

_______________________________  =  -.84                     multiply both sides by 4.2

4.2

mass we are trying to find - 55 =  -3.528        add  55 to both sides

mass we are trying to find  =  51.472   ≈   51.5 g      [ first answer ]

EDIT TO CORRECT A PREVIOUS ERROR  !!!

Apr 5, 2019
edited by CPhill  Apr 5, 2019
#5
+1534
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Wouldnt we need to subtract 1-0.80 ? and wouldnt the value be negatitive ?

jjennylove  Apr 5, 2019
edited by jjennylove  Apr 5, 2019
#6
+107098
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Ah yes...I misread that one...let me do an edit

CPhill  Apr 5, 2019
#3
+84
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What cphill said

Apr 5, 2019
#4
+107098
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Second one

[ age we are looking for  - mean ]

____________________________  =   z score

std dev

[age we are looking for - 32  ]

___________________________  =  -1.2                 multiply both sides by  6.2

6.2

age we are looking for - 32  = -7.44           add 32 to both sides

age we are looking for  = 24.56  =  24.6  rounded to nearest tenth

Apr 5, 2019