Statistics: Informed Decisions Using Data (4th Edition)

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

Chapter 11 - Section 11.3 - Consumer Reports - The High Cost of Convenience - Page 566: d

Answer

There is no evidence to conclude that the boxed version performs better than the traditional roll. Since the traditional roll has a significantly lower price than the boxed version with a performance of about the same than the boxed version, it is recommended to buy the traditional roll.

Work Step by Step

$x ̅_1,n_1~and~s_1$ refer to the boxed version and $x ̅_2,n_2~and~s_2$ refer to the roll. $t_0=\frac{(x ̅_1-x ̅_2)-(µ_1-µ_2)}{\sqrt {\frac{s^2_1}{n_1}+\frac{s^2_2}{n_2}}}=\frac{(0.9717-1.0200)-0}{\sqrt {\frac{0.0538^2}{6}+\frac{0.0942^2}{6}}}=-1.091$ Left-tailed test: $n=6$ (use the smaller value of $n$), so: $d.f.=n-1=5$ $P$-value $=P(t\lt t_0)=P(t\lt-1.091)=P(t\gt1.091)$ For $d.f.=5$ and the area to area in right tail equals to 0.15: $t=1.156$ For $d.f.=5$ and the area to area in right tail equals to 0.20: $t=0.920$ So, $0.15\lt P$-value $\lt0.20$. Since $P$-value $\gt α$, for any usual $α$ (0.01, 0.05, 0.10), we do not reject the null hypothesis.
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