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Statistics for Decision- Making in Business - Maricopa Community ...

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√<br />

The lower limit is:<br />

√<br />

And the upper limit is:<br />

Thus, we are 95% confident that the true average age <strong>in</strong> this town is between 23.4 and 27.8.<br />

Notice that this is not very much different than our simulated confidence <strong>in</strong>terval of 23.6 to 27.5.<br />

So, which is more precise This is arguable, but it is difficult to argue with empirical data.<br />

Personally, I prefer the bootstrap confidence <strong>in</strong>terval we ran earlier. My reason<strong>in</strong>g is that a<br />

distribution of means is asymptotically normal, mean<strong>in</strong>g that, under <strong>in</strong>f<strong>in</strong>itely many sampled<br />

units, the distribution would be exactly normal. This is very theoretical and not always valid.<br />

For now, we will compare both.<br />

For the 99% confidence <strong>in</strong>terval, theory produces the follow<strong>in</strong>g:<br />

√<br />

We would now simply adjust the number of standard deviations to 2.756:<br />

Lower limit:<br />

√<br />

<strong>Statistics</strong> <strong>for</strong> <strong>Decision</strong>-<strong>Mak<strong>in</strong>g</strong> <strong>in</strong> Bus<strong>in</strong>ess © Milos Podmanik Page 199

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