+0  
 
0
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avatar+1534 

Please explain so I understand

 Apr 5, 2019
 #1
avatar+1534 
+1

 

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
avatar+107098 
0

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  !!!

 

 

 

cool cool cool 

 Apr 5, 2019
edited by CPhill  Apr 5, 2019
 #5
avatar+1534 
+1

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
avatar+107098 
+1

Ah yes...I misread that one...let me do an edit

 

cool cool cool

CPhill  Apr 5, 2019
 #3
avatar+84 
+2

What cphill said

 Apr 5, 2019
 #4
avatar+107098 
0

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

 

 

cool cool cool

 Apr 5, 2019

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