Question

Lumber intended for building houses and other structures must be monitored for strength. A random sample of 25 specimens of Southern Pine is selected, and the mean strength is calculated to be 3700 pounds per square inch.  Strengths are known to follow a Normal distribution with a standard deviation of 500 pounds per square inch. A 90% confidence interval for the true mean strength of Southern Pine is:

Select one:

a. (3200, 3647)

b. (3402, 3794)

c. (3536, 3865)

d. (3400, 3800)

Answer 1

0.08 X = 3700, p=soo, 7=25 -|- - 0 invnory (0-08,0,1) = -1.640 90%.c1 . #+Z/ M 3700 +1.648 Go 500 Jas (3536, 38.65 ) Mihoon '" option fe