Statistics: Informed Decisions Using Data (4th Edition)

Published by Pearson
ISBN 10: 0321757270
ISBN 13: 978-0-32175-727-2

Chapter 11 - Section 11.4 - Assess Your Understanding - Applying the Concepts - Page 575: 19a

Answer

$F_0\gt F_{1-α,n_1-1,n_2-1}$: null hypothesis is rejected. There is enough evidence to conclude that the variability in wait time in the single line is less than that for the multiple lines.

Work Step by Step

$s_1,n_1~and~d.f._1$ refer to single line and $s_2,n_2~and~d.f._2$ refer to multiple lines. $H_0:~σ_1=σ_2$ versus $H_1:σ_1\ltσ_2$ $s_1=\sqrt {\frac{∑(x_{1_i}-x ̅_1)^2}{n_1-1}}=0.574$ $s_2=\sqrt {\frac{∑(x_{2_i}-x ̅_2)^2}{n_2-1}}=1.012$ $F_0=\frac{s_1^2}{s_2^2}=\frac{0.574^2}{1.012^2}=0.32$ $d.f_1=n_1-1=20-1=19$ $d.f_2=n_2-1=20-1=19$ Left-tailed test: $F_{α,n_1-1,n_2-1}=F_{0.05,19,19}=2.12$ (According to table VIII, for $d.f._1=20$, the closest value to 19, $d.f._2=20$, the closest value to 19, and area in the right tail = 0.05) $F_{1-α,n_1-1,n_2-1}=F_{0.95,19,19}=\frac{1}{F_{0.05,19,19}}=\frac{1}{2.12}=0.47$ Since $F_0\lt F_{1-α,n_1-1,n_2-1}$, we reject the null hypothesis.
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