yashar806
Weights of apples grown in an orchard are known to follow a normal distribution with mean 160 grams. It is known that approximately 99.7% of apples have weights between124 and 196 grams. What is the standard deviation of weights of all apples grown in the orchard?
Delete
Share
This Question is Closed
tomo
Best Response
You've already chosen the best response.
0
|dw:1363376606947:dw|
yashar806
Best Response
You've already chosen the best response.
0
but i cant get the right answer
yashar806
Best Response
You've already chosen the best response.
0
i used that that formula
tomo
Best Response
You've already chosen the best response.
0
|dw:1363376747863:dw|
tomo
Best Response
You've already chosen the best response.
0
z1 = (124-160)/sigma
z2 = (196-160)/sigma
1-z1-z2 = (99.7)/100
tomo
Best Response
You've already chosen the best response.
0
i have to leave, but I think that should help you find the answer
amistre64
Best Response
You've already chosen the best response.
0
dont we just need one of those to determine sigma?
amistre64
Best Response
You've already chosen the best response.
0
\[z=\frac{x-\bar x}{sd}\]
\[sd=\frac{x-\bar x}{z}\]
yashar806
Best Response
You've already chosen the best response.
0
i got confused
yashar806
Best Response
You've already chosen the best response.
0
why we need to 1- them
amistre64
Best Response
You've already chosen the best response.
0
or rather, we dont have the z value explicitly do we
yashar806
Best Response
You've already chosen the best response.
0
we do have z
yashar806
Best Response
You've already chosen the best response.
0
99.7%
amistre64
Best Response
You've already chosen the best response.
0
|dw:1363377005023:dw|
amistre64
Best Response
You've already chosen the best response.
0
we have an implicit z, we can either use the zscore of .3/2 .. or 99.7+.3/2
yashar806
Best Response
You've already chosen the best response.
0
what would be answer?
amistre64
Best Response
You've already chosen the best response.
0
does that make sense?
99.7% is inbetween those values, so the proper zscore has to be adjusted.
use z(.9985), at x=196
or, z(.0015), at x=124
yashar806
Best Response
You've already chosen the best response.
0
yes
amistre64
Best Response
You've already chosen the best response.
0
id prolly use the 196 version
amistre64
Best Response
You've already chosen the best response.
0
can you tell me the zscore of .9985?
yashar806
Best Response
You've already chosen the best response.
0
2.96
amistre64
Best Response
You've already chosen the best response.
0
i agree
soo, sd= (196-160)/2.96
yashar806
Best Response
You've already chosen the best response.
0
oh, i got it
yashar806
Best Response
You've already chosen the best response.
0
can we use both of them?
amistre64
Best Response
You've already chosen the best response.
0
both of what?
yashar806
Best Response
You've already chosen the best response.
0
z1 = (124-160)/sigma
z2 = (196-160)/sigma
yashar806
Best Response
You've already chosen the best response.
0
like that
amistre64
Best Response
You've already chosen the best response.
0
we can, the sd will be negative for the z1 equation
and the percentage at z1 is (.0015), iinstead of (.9985)
yashar806
Best Response
You've already chosen the best response.
0
thats wht i used initially
yashar806
Best Response
You've already chosen the best response.
0
but i got wrong answer
amistre64
Best Response
You've already chosen the best response.
0
one chk would be to do (124-160)/12.1622 and see if its about -.0015 :)
amistre64
Best Response
You've already chosen the best response.
0
hmm, i get -2.96
is 160 by chance the average of 124 and 196?
amistre64
Best Response
You've already chosen the best response.
0
.... yep