SOLUTION: A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 265.9-cm and a standard deviation of 1.6-cm. For shipment, 30 steel rods are bu

Question 1155693: A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 265.9-cm and a standard deviation of 1.6-cm. For shipment, 30 steel rods are bundled together.
Find the probability that the average length of a randomly selected bundle of steel rods is between 265.4-cm and 266.8-cm.
P(265.4-cm < M < 266.8-cm)
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
use a z-test where z=(xbar-mean)/sigma/sqrt(n)
The denominator is the SE and is 1.6/sqrt(30)=0.292
z=-0.5/0.292 and .9/.292 or between -1.71 and 3.08
that probability is 0.9553.
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