Answer:
[tex](16.648, 21.352)[/tex]
Step-by-step explanation:
Let X be the accelerated life test on a large number of type-D alkaline batteries revealed that the mean life for a particular use before they failed
X is NOrmal with mean =19, sigma = 1.2
For 95% critical value = ±1.96
Margin of error = ±1.96*1.2
=±2.352
Confidence interval 95% = Mean ±2.352
=(16.648, 21.352)