5. The owner of a fish market determined that the average weight for a catfish i
ID: 3274350 • Letter: 5
Question
5. The owner of a fish market determined that the average weight for a catfish is 3.6 pounds with a standard deviation of 0.8 pound. Assume the weights of catfish are normally distributed.
PLEASE SHOW WORK AND FORMULAS USED. EXCEL, ETC IF NECESSARY
a. What is the probability that a randomly selected catfish will weigh more than 4.8 pounds?
b. What is the probability that a randomly selected catfish will weigh between 3 and 5 pounds?
c. A randomly selected catfish will weigh more than x pounds to be one of the top 5% in weight. What is the value of x?
d. A randomly selected catfish will weigh less than x pounds to be one of the bottom 20% in weight. What is the value of x?
e. Above what weight in (pounds) do 87.70% of the weights occur?
f. What is the probability that a randomly selected catfish will weigh less than 3.2 pounds?
g. Below what weight (in pounds) do 83.4% of the weights occur?
Explanation / Answer
a.
Since =3.6 and =0.8 we have:
P ( X>4.8 )=P ( X>4.83.6 )=P ( X>4.83.60.8)
Since Z=x and 4.83.60.8=1.5 we have:
P ( X>4.8 )=P ( Z>1.5 )
Use the standard normal table to conclude that:
P (Z>1.5)=0.0668
b.
Since =3.6 and =0.8 we have:
P ( 3<X<5 )=P ( 33.6< X<53.6 )=P ( 33.60.8<X<53.60.8)
Since Z=x , 33.60.8=0.75 and 53.60.8=1.75 we have:
P ( 3<X<5 )=P ( 0.75<Z<1.75 )
Use the standard normal table to conclude that:
P ( 0.75<Z<1.75 )=0.7333
c. Top 5%
z from table =1.645
(x-3.6)/0.8 = 1.645
Solve for x
= 4.916
d.
z from table =0.84
(x-3.6)/0.8 = 0.84
Solve for x
= 2.927
e.
87.7% of the weights
z from table =1.21
(x-3.6)/0.8 = 1.21
Solve for x
= 4.569
f.
Since =3.6 and =0.8 we have:
P ( X<3.2 )=P ( X<3.23.6 )=P (X<3.23.60.8)
Since x=Z and 3.23.60.8=0.5 we have:
P (X<3.2)=P (Z<0.5)
Use the standard normal table to conclude that:
P (Z<0.5)=0.3085
g. below 83.4%
z from table =0.97
(x-3.6)/0.8 = 0.97
Solve for x
= 4.376
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