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

question 37

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$ $\text { t-Test: Assuming Unequal Variances }$

$\begin{array}{l}\begin{array} { lrr } &\text { takeJet } &\text { HogJet } \\\text { Mean } & 80.3368 & 82.4669 \\\text { Variance } & 0.7178 & 4.7385 \\\text { Observations } & 10 & 10 \\\text { Pooled Variance } & 2.7282 & \\\text { Hypothesized Diff } & 0.0000 & \\\text { df } & 18 \\\text { t Stat } & -2.8837 \\\text { P(T eat) one-tail } & 0.0049 \\\text { t Critical one-tail } & 1.7341 \\\text { P(T =-t) two-tail } & 0.0099 \\\text { t Critical two-tail } & 2.1009 &\end{array}\begin{array} { lrr} &\text { takeJet } &\text { HogJet } \\\text { Mean } & 80.3368 & 82.4669 \\\text { Variance } & 0.7178 & 4.7386 \\\text { Observations } & 10 & 10 \\\text { Hypothesized Diff } & 0 & \\\\\text { df } & 12 \\t \text { Stat } & -2.8837 \\\text { P(T } \text { ett ) one-tail } & 0.0069 \\t \text { Critical one-tail } & 1.7823 \\\mathrm{P}(\mathrm{T}<=\mathrm{t}) \text { two-tail } & 0.0137 \\\mathrm{t} \text { Critical two-tail } & 2.1788\end{array}\end{array}$
If we switched from ? = .05 to ? = .005 in a two-tailed test of means, our assumption about variances (assumed equal or assumed unequal) would:

• A)affect the decision.
• B)not affect the decision.
• C)require a new analysis.

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