Question

The mean time between failures (in hours) for a Telektronic Company radio used in light aircraft is 420. After 15 new radios were modified in an attempt to improve reliability, tests were conducted to measure the times between failures. The mean time for 15 new radios is 442.2 and the standard deviation (S) is 44.0. Test the claim that the modified radios have a mean greater than 420.0 using a significance level 0.025.

Answer 1

Solution:

This a right (One) tailed test.

The null and alternative hypothesis is,  

Ho: 420

Ha: 420

The test statistics,

t =( - )/ (s /n)

= ( 442.2 - 420 ) / ( 44 / 15 )

= 1.954

P-value = 0.035

The p-value is p = 0.035 > 0.025 it is concluded that fail to reject the null hypothesis.

There is not sufficient evidence to claim that the modified radios have a mean greater than 420.0 using a significance level 0.025.