Statistics 1 Normal Distribution Question Help ASAP!!!

Hello
Can any1 help me with this question:
"The weights of hens' eggs are normally distributed with a mean of 65 grams and standard deviation of 10 grams. Eggs which weigh less than 56.5 grams are considered small. Those eggs which are not classified as small are classified as medium or large in equal proportion.
Calculate to 1dp the weight above which eggs are classified as large"

Reply 1

Lemonsoul

ramdayal

Been a while since I covered this so I might not be correct but:

P(X<56.5) = P(egg being small) = phi((56.5-65)/10) = phi(-0.85)
= 1 - phi(0.85) = 0.1977 (using stats tables)

P(egg being medium or large) = 1 - P(small) = 0.8023

As: P(medium) = P(large)
so: P(large) = 0.8023/2 = 0.40115

Call 'A' the weight above which eggs are classified as large

P(X>A) = 0.40115
P(X<A) = 1 - 0.40115 = 0.59885

phi((A-65)/10) = 0.59885 = roughly phi(0.25) (using stats tables)

(A-65)/10 = 0.25
A = 67.5 grams

Reply 2

Kolya

nhdb13 's answer is correct.

cheers

hello
can anyone help me wiv this question..........
the thickness of some sheets of wood follows a normal distribution with mean and standard deviation,,96%of the sheets will go through 8 mm gauge while only 1.7% will go through a 7 mm gauge,,find mean and standard deviation!!!
plz help me!!!!!!!!

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