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

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When answer<strong>in</strong>g these questions, it is fairly useful to fully organize the data by provid<strong>in</strong>g all<br />

totals:<br />

Smoker/Lung Cancer Yes No Smoker TOTALS<br />

Yes 688 650 1,338<br />

No 21 59 80<br />

Lung Cancer TOTALS: 709 709 1,418<br />

1. S<strong>in</strong>ce there is a total of 1,418 <strong>in</strong>dividuals be<strong>in</strong>g considered and, of those, 709 developed<br />

lung cancer,<br />

( )<br />

We must be careful <strong>in</strong> us<strong>in</strong>g this probability as it doesn‟t really reveal anyth<strong>in</strong>g about the<br />

l<strong>in</strong>k between lung cancer and smok<strong>in</strong>g, s<strong>in</strong>ce 709 patients with lung cancer and 709<br />

without lung cancer were chosen to participate <strong>in</strong> the study to beg<strong>in</strong> with. This is a<br />

probability that was fixed by the researchers.<br />

2. There is a total of 1,338 <strong>in</strong>dividuals <strong>in</strong> the study that smoke (we are limited to the<br />

smokers only, per the way the question is stated). Of those <strong>in</strong>dividuals, 688 have lung<br />

cancer.<br />

( )<br />

Slightly over half of the patients who are smokers developed lung cancer. This number is<br />

frighten<strong>in</strong>gly large. Be<strong>for</strong>e we jump the gun <strong>in</strong> assum<strong>in</strong>g that smok<strong>in</strong>g is the culprit here,<br />

we should probably consider what happens with nonsmokers.<br />

3. There is a total of 80 nonsmokers <strong>in</strong> the group. Of them, 21 developed lung cancer.<br />

( )<br />

Slightly more than one-fourth of non-smokers developed lung cancer. This number<br />

appears to be significantly less severe than <strong>for</strong> the smokers. We speculate (but did not<br />

prove) that smok<strong>in</strong>g <strong>in</strong>creases the likelihood that one will develop lung cancer.<br />

4. There are 709 patients with lung cancer. Of these, 688 smoke.<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 86

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