Unformatted text preview: . The breaking strength of a rivet has a mean value of 10,000 psi, and a
standard deviation of 500 psi.
a) What is the probability that the sample mean breaking strength for a random sample of 40
rivets is between 9900 and 10,200?
Since n > 30, we can assume that we have a normal distribution. b) If the sample size had been 15 rather than 40, could the probability requested in part (a) be
calculated from the given information?
No. Since 15 < 30, we can no longer assume a normal distribution. Without knowing the distribution, we
cannot calculate a probability. 1 (2.5 pts.) 5.66 abe (p.222). If two loads are applied to a cantilever beam as shown below, the
bending moment at 0 due to the loads is a1X1 + a2X2. a) Suppose that X1 and X2 are independent rv’s with means 2 and 4 kips, respectively, and
standard deviations 0.5 and 1.0 kip, respectively. If a1 = 5 ft and a2 = 10 ft, what is the expected
bending moment and what is the standard deviation of the bending moment?
a1 = 5
a2 = 10 E(X1) = 2
E(X2) = 4 = 0.5...
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