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Can you explain why , so I understand?

 

 

2) A normal distribution has a mean of 102 and a standard deviation of 2.9.

What is the z-score of 105?

Enter your answer, rounded to the nearest hundredth.

Answer is 1.03

 Apr 5, 2019
edited by jjennylove  Apr 5, 2019
 #1
avatar+99580 
+2

Don't know about the first....but......here's the second one....

 

[ 105 - 102 ]

__________  =   

       2.9

 

 

   3

____  =

  2.9 

 

1.03

 

 

cool cool cool

 Apr 5, 2019
 #2
avatar+812 
0

 

This one too if you can . If not I understand

 Apr 5, 2019
 #3
avatar+99580 
+2

[ 165 - 176 ]

_________    =   z score we are looking for

     11.4

 

-11

____     ≈    -.96

11. 4

 

Looking at the table here : http://www.z-table.com/

 

This corresponds to   .1685

 

So....about  16.85%  of the 120 will weigh < 165 lbs

 

So.....this means that  120 ( 1 - .1685)   ≈  99.78  will weigh > 165 lbs

 

So    99.78  will round to 100

 

Good job !!!

 

cool cool cool

 Apr 5, 2019
 #4
avatar+812 
0

Im so glad Im understanding these! Im going to be uplaoding more to double check not sure if you would like to but if you do that would be great.

 

Here is another one.

 

Now this one I was a bit confused but maybe I did it correctly

jjennylove  Apr 5, 2019
 #5
avatar+812 
0

 

I got 68.08 but what does this mean exactly ? That all the scores are below 68 ?

jjennylove  Apr 5, 2019
 #8
avatar+99580 
+2

16%  corresponds to  either   a   z score of  -.99   OR  a z score of 1

 

So   we either have that

 

[ score - 76 ]

___________  =  -.99      multiply both sides by 8

       8

 

score - 76  = -7.92       add  76 to both sides

 

score  = 68.08......which means that 16% will be below about 68

 

OR

 

[ score - 76 ]

__________   =   1             multiply both sides by 8

       8  

 

 

score - 76  =  8       add  76 to both sides

 

score  =  84     .....this means that 16% will be above  84 

 

But...since this isn't one of your choices......68 is correct

 

[ Note that the 16% could be anywhere.   for example....it could also mean the 16% "cluster" on either side of the mean ] 

 

 

cool cool cool

CPhill  Apr 5, 2019
edited by CPhill  Apr 5, 2019
edited by CPhill  Apr 5, 2019
 #12
avatar+812 
0

Since your online again, I was kind of confused on this one as to why you said " Since this isnt your choice it is 68"

jjennylove  Apr 5, 2019
 #13
avatar+812 
0

Is that jsut for the other question ?

jjennylove  Apr 5, 2019
 #14
avatar+812 
0

where did you get 18% isnt it 16%?

jjennylove  Apr 5, 2019
 #15
avatar+99580 
+1

Sorry....I mis-read that....it should be 16%

 

Can you take it from there or do you want me to edit my answer to check???/

 

cool cool cool

CPhill  Apr 5, 2019
 #16
avatar+812 
0

Could you edit your answer? Sorry just to double check

jjennylove  Apr 5, 2019
 #17
avatar+99580 
+2

Done!!!!

 

Your answer of 68  is still good    !!!

 

 

cool cool cool

CPhill  Apr 5, 2019
 #6
avatar+99580 
+2

OK

 

30%  = .30    which corresponds to a z score ≈ -.52

 

So....we have

 

[ weight we are looking for - mean ]

_____________________________   =   -.52

              std dev 

 

[ weight we are looking for - 143 ]

___________________________     =  -.52           multiply both sides by  4.2

               4.2

 

 

weight we are looking for - 143    = -2.184         add 143 to oth sides

 

weight we are looking for   = 140.8 g    (round to 141 g )

 

Good JOB !!!....I think you got it !!!

 

 

cool cool cool

 Apr 5, 2019
 #7
avatar+812 
+1

Yay! I am so happy im understanding it thank you for your detialed explanations !

jjennylove  Apr 5, 2019
 #9
avatar+812 
+1

I see it now! That was a confusing but from your explaintions it makes more sense. smiley Thank you for your help CPhill

jjennylove  Apr 5, 2019
edited by jjennylove  Apr 5, 2019
 #10
avatar+99580 
+1

OK.....glad to help.....sorry I don't know the answer(s) to the first one....I hate to "guess" and maybe give incorrect answers......

 

 

cool coolcool

CPhill  Apr 5, 2019
 #11
avatar+812 
+1

No its okay you have been plenty of help maybe ElectricPavlov can help me on it when he gets online. Im gonna repost the question in case he doesnt see it here. Thank you againlaugh

jjennylove  Apr 5, 2019

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