Question

13. . Aircraft engine driven hydraulic pumps have an established mean time to failure of 5,500 hours. A sample of 53, from a different vendor, gave a mean life of 6,823 hours and a standard deviation of 564 hours. Using a 5% significance level, test the claim that the new vendor has significantly improved MTBF of hydraulic pumps.

Answer 1

H0: <= 5500

HA: > 5500

Test statistics

t = (​​​​​​ - ) / (S / sqrt(n))

= (6823 - 5500) - ( 564 / sqrt(53) )

= 17.08

Critical value at 0.05 significance level with 52 = 1.675

Since test statistics > 1.675, Reject H0.

We conclude at 0.05 level that we have sufficient evidence to support the claim that the new vendor has

significantly improved MTBF of hydraulic pumps.