Answer (Choose 1 answer)
A (See picture)
A. (394; 406)
B. (392; 408)
C. (393; 407)
D. (395; 405)
E. None of the other choices is correct
A random sample of 79 light bulbs had a mean life of 400 hours. Construct a 90%confidence interval for the mean life of all light bulbs of this type. Assume that the standard deviation of all light bulb's life is known to be 28 hours.
Let Z0.05 1.645; Zo.1 1.282.
Exit 34
