8-5 p411 n14
Original claim: The mean life span of desktop PCs is less than 7 years
μ < 7
The Null Hypothesis
H0: μ = 7
The Alternate Hypothesis
H1: μ < 7
A sample of n = 21 has 20 degrees of freedom.
For a left tailed test and a level of significance, α = 0.05
tcritical = -1.725
Data:
x_= 6.8 and s = 2.4
ttest = (6.8-7) ⁄ (2.4 ⁄ √21) = -0.382
Because -0.382 is NOT in the Critical Region, we Fail to Reject the Null Hypothesis and the statistical analysis of the data can NOT support the original claim.
Conclusion:
There is NOT sufficient sample evidence to support the claim that The mean life span of desktop PCs is less than 7 years