Question

Nacirema Airlines is buying a fleet of new fuel-efficient planes. The HogJet and the LitheJet both meet their price and performance needs, and both planes meet EPA noise guidelines. However, the quieter plane is preferred. Each plane is flown through a typical takeoff and landing sequence 10 times, while remote sensors at ground level record the noise levels (in decibels).
The average noise levels from these 10 flights are 80.34 for LitheJet and 82.47 for HogJet, the pooled variance is reported to be equal to 2.73.
Is there enough evidence to conclude that LitheJet planes are quieter?

Show how to calculate test statistics, p val, etc for conclusion.

Answer 1

n1 =10, = 80.34

n2= 10, = 82.47

pooled variance = = 2.73

pooled standard deviation = Sp=1.65227

Null and alternative hypothesis is

Ho:

Ha:

formula for test statistics is

t = -2.883

test statistics =-2.883

now calculate p-value for left tailed test with df= n1+n2-2 = 10+10-2 = 18

using t table we get

P-Value = 0.0050

decision rule is

Reject Ho if (P-Value) < ( )

here  

(P-Value= 0.0050) < ( = 0.05)

Hence,

Null hypothesis is rejected.

Conclusion:

Therefoe there is enough sufficient evidence to conclude that LitheJet planes are quieter at = 0.05.