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 574: 15

Answer

$F_0\gt F_{\frac{α}{2},n_1-1,n_2-1}$: null hypothesis is rejected. There is enough evidence to conclude that the standard deviation time to earn a bachelor’s degree is different between the two groups.

Work Step by Step

$H_0:~σ_1=σ_2$ versus $H_1:σ_1\neσ_2$ $F_0=\frac{s_1^2}{s_2^2}=\frac{1.162^2}{1.015^2}=1.31$ $d.f_1=n_1-1=268-1=267$ $d.f_2=n_2-1=1145-1=1144$ Two-tailed test: $F_{\frac{α}{2},n_1-1,n_2-1}=F_{0.025,267,1144}=1.29$ (According to table VIII, for $d.f._1=120$, the closest value to 267, $d.f._2=1000$, the closest value to 1144, and area in the right tail = 0.025) $F_{1-\frac{α}{2},n_1-1,n_2-1}=F_{0.975,267,1144}=\frac{1}{F_{0.025,267,1144}}=\frac{1}{1.29}=0.78$ Since $F_0\gt F_{\frac{α}{2},n_1-1,n_2-1}$, we reject the null hypothesis.
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