Answer
n = $(\frac{ z_α/_2 * σ}{E})^{2}$
When Confidence interval = 99%
α= 1-0.99 = 0.01.
α/2 = 0.005
1-0.005 = 0.995
From the table,
$z_α/_2$ = 2.58
Since z_α/2 = 2.58 and E = 0.5 hours, σ = 2.6 hours
$(\frac{ z_α/_2 * σ}{E})^{2}$
= $[ $\frac{2.58 * 2.6 }{0.5}$ ] ^{2}$
=$(13.416 )^{2}$
=179.9891 = 180 sample
To be 99% confident that the true mean differs from the sample mean by 0.5 hour, 180 sample must be needed.
Work Step by Step
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