Young's modulus is a quantitative measure of stiffness of an elastic material. Suppose that for metal sheets of a particular type, its mean value and standard deviation are 75 GPa and 1.7 GPa, respectively. Suppose the distribution is normal. (Round your answers to four decimal places.) Required:
a. Calculate P(79 <= P <= 81) when n = 25.
b. How likely is it that the sample mean diameter exceeds 81 when n = 36?

a) P(79 <= P <= 81) = 0.9968

b) P( X >  81 ) = 0.0002

Step-by-step explanation:

mean value = 75 GPa

standard deviation = 1.7 GPa

a) Determine P(79 <= P <= 81)

given that : n = 25

attached below is the detailed solution

P(79 <= P <= 81) = 0.9968

b) Determine how likely the sample mean diameter will exceed 81

given that n = 36

mean diameter = 81

P( X >  81 ) = 0.0002

yes

yes yes yes

x > 1.3

step by step:

8.5−0.9x> 9.8−1.9x

step 1: simplify both sides of the inequality.

−0.9x+8.5> −1.9x+9.8

step 2: add 1.9x to both sides.

−0.9x+8.5+1.9x> −1.9x+9.8+1.9x

1x+8.5> 9.8

step 3: subtract 8.5 from both sides.

1x+8.5−8.5> 9.8−8.5

1x> 1.3

step 4: divide both sides by 1.

1x/1 > 1.3/1