Answer: a) (1008.34,1019.658) b) (1009.24,1018.76)
Step-by-step explanation:
Since we have given that
n = 75
mean = 1014 hours
Standard deviation = 25 hours
At 95% two sided , z = 1.96
So, confidence interval would be
(b) Construct a 95% lower confidence bound on the mean life.
z = 1.65
So, confidence interval would be
Hence, a) (1008.34,1019.658) b) (1009.24,1018.76)