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Problem 07 - 30
National Partamiento Co.
Months
in
Service
Number
Installed
Number
Failed
Number Not
Failed
Cumulative
Failures
Month x
Failures
Months in
Service
Monthly Failure Rate
Cumulative
Failure Rate
1 24440 1 24439 1 1 1 0.00004092 0.00004092 Regression on number of units failed by month
2 24439 3 24436 4 6 2 0.00012275 0.00016367
10 24331 30 24301 139 300 10 0.00123299 0.00570133 Standard Error 1.828835338
11 24301 31 24270 170 341 11 0.00127567 0.00697700 Observations 12
12 24270 29 24241 199 348 12 0.00119489 0.00817189
Totals 199 1708 Totals ANOVA
df SS MS F Significance F
Regression 1 1201.47028 1201.47028 359.2227411 3.62759E-09
Average failure rate (lambda) = 0.000680109 Residual 10 33.44638695 3.344638695
Total 11 1234.916667
Months
in
Service
Number
Installed
Number
Failed
Number Not
Failed
Cumulative
Failures
Monthly
Failure Rate
35 22793 99 22694 1746 0.00434344
36 22694 102 22592 1848 0.00449458
Percent failure over 36 months =
7.56
Projected failures using lambda = (0.00068011*36)= 0.02448396
0
5
10
15
0 2 4 6 8 10 12 14
Number Failed
Months in Service
Number Failed
Predicted Number Failed
