In: Statistics and Probability
. Suppose a PC manufacturer wants to evaluate the performance of its hard disk memory system. One measure of performance is the average time between failures of the disk drive. To estimate this value, a quality control engineer recorded the time between failures for a random sample of 49 disk-drive failures. A summary of the sample statistics was that x-bar = 5,790.36 hours and with sample standard deviation s = 224 hours. Estimate the true mean time between failures with a 90% CI.
We have given that,
Sample mean = 5790.36 hours
Sample standard deviation =224 hours
Sample size = 49
Level of significance=1-0.90= 0.1
Degree of freedom =48
t critical value is (by using t table)=
1.6772
Confidence interval formula is
=(5736.69,5844.03)
Lower confidence limit= 5736.69 hours
Upper confidence limit= 5844.03 hours