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619snake
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Homework Statement
the weight of items produced by a production line is normally distributedwith a mean of 12 ounces and a standard deviation of 2 ounces.
a. what is the probability that a randomly selected item will weight between 8 and 16 ounces? (DONE)
b. what is the probability that a randomly selected item will weight over 20 ounces? (DONE)
c. Suppose that quality control requires the weight of items to be within 8 and 16 ounces. You select 7 items at random (each item is independent). What is the probability that 3 of the items will fulfill quality control requirements. (DONE BUT HAVE DOUBTS)
d. find the probability that a randomly selected item has a weight that is greater than 14 or smaller than 10. (STUCK IN THIS ONE)
2. Related formulas
if x is BIN
p(x=k) = (n!)/((n-k)!(k!)) * [tex]\pi[/tex]^k * (1-[tex]\pi[/tex])^(n-k)
mean = n[tex]\pi[/tex]
variance = n[tex]\pi[/tex](1-[tex]\pi[/tex])
if x is N(µ,[tex]\sigma[/tex]), then z=(x-µ)/([tex]\sigma[/tex]) is N(0,1)
The Attempt at a Solution
a. x~n (µ=12, [tex]\sigma[/tex]=2)
p(8<x<16)
p(x<16) - p(x<8)
z=(16-12)/2 z=(8-12)/2
z=2 z= -2
p(z<2)-p(z<-2)
=.9772-.0228
=.9544
b.P(x>20)
z=(20-12)/2
z=4
p(z>4)= 1
c.x~binomial (µ=7, [tex]\sigma[/tex]=.95)
p(x=3)
p(x=K)=[tex](3!)/(3!)(7-3)![/tex](.95)^3 (1-.95)^4
.
.
.
x=0.000187551
d. I have no idea how to deal with this one
I think I have to use the mean and standard deviation of the problem
(µ=12, [tex]\sigma[/tex]=2)
P(x<10) or P(x>14)
Hope you people can help me