In: Math
An article suggested that yield strength (ksi) for A36 grade steel is normally distributed with μ = 45 and σ = 4.5.
(a) What is the probability that yield strength is at most 40? Greater than 63? (Round your answers to four decimal places.)
at most 40 | ||
greater than 63 |
(b) What yield strength value separates the strongest 75% from the
others? (Round your answer to three decimal places.)
ksi
µ = 45
sd = 4.5
a)
= P(Z < 1.11)
= 0.8665
b)
= P(Z > 4)
= 1 - P(Z < 4)
= 1 - 1
= 0
b)
or, x = 45 - 0.67 * 4.5
or, x = 41.985 (ans)