Nacirema Airlines Is Buying a Fleet of New Fuel-Efficient Planes $\quad$

Multiple Choice

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 table below summarizes the sound level tests using Excel's default level of significance (? = 0.05) . $\quad$$\quad$$\text { t-Test: Assuming Equal Variances }$ $\quad$$\quad$$\quad$$\quad$ $\text { t-Test: Assuming Unequal Variances }$

$\begin{array}{l}\begin{array} { lrr } &\text { takeJet } &\text { HogJet } \\\text { Mean } & 80.3368 & 82.4669 \\\text { Variance } & 0.7178 & 4.7385 \\\text { Observations } & 10 & 10 \\\text { Pooled Variance } & 2.7282 & \\\text { Hypothesized Diff } & 0.0000 & \\\text { df } & 18 \\\text { t Stat } & -2.8837 \\\text { P(T eat) one-tail } & 0.0049 \\\text { t Critical one-tail } & 1.7341 \\\text { P(T =-t) two-tail } & 0.0099 \\\text { t Critical two-tail } & 2.1009 &\end{array}\begin{array} { lrr} &\text { takeJet } &\text { HogJet } \\\text { Mean } & 80.3368 & 82.4669 \\\text { Variance } & 0.7178 & 4.7386 \\\text { Observations } & 10 & 10 \\\text { Hypothesized Diff } & 0 & \\\\\text { df } & 12 \\t \text { Stat } & -2.8837 \\\text { P(T } \text { ett ) one-tail } & 0.0069 \\t \text { Critical one-tail } & 1.7823 \\\mathrm{P}(\mathrm{T}<=\mathrm{t}) \text { two-tail } & 0.0137 \\\mathrm{t} \text { Critical two-tail } & 2.1788\end{array}\end{array}$
In a left-tailed test comparing the means at ? = .05, we would:

A) not reject H₀.
B) reject H₀.
C) have insufficient information to make a decision.