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

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That is, the probability that the capacitor fails is dependent upon the resistor fail<strong>in</strong>g. Fill<strong>in</strong>g <strong>in</strong><br />

what we know:<br />

Divid<strong>in</strong>g gives,<br />

( )<br />

( )<br />

Thus, there is a 77.9% chance the capacitor fails if the resistor fails. The resistor is an <strong>in</strong>tegral<br />

part <strong>in</strong> this device. The likelihood of the capacitor fail<strong>in</strong>g <strong>in</strong>creases, if the resistor fails first.<br />

The above examples br<strong>in</strong>gs up a useful result.<br />

Calculat<strong>in</strong>g the Conditional Probability of A given B<br />

S<strong>in</strong>ce ( ) ( ) ( )<br />

We have that,<br />

( )<br />

( )<br />

( )<br />

Example 6: In a demographic study of a small, it is found that 5% of the adult residents are<br />

unemployed and liv<strong>in</strong>g at or below poverty level. A total of 8% are unemployed. What is the<br />

probability that a person <strong>in</strong> this town is liv<strong>in</strong>g at or below the poverty level, given that they are<br />

unemployed Interpret the mean<strong>in</strong>g of your answer.<br />

SOLUTION:<br />

Lett<strong>in</strong>g = a person lives at or below the poverty level and = a person is unemployed, we<br />

would like to know, ( )<br />

We have that ( ) ( ) . Thus:<br />

( )<br />

This says that, if a person is unemployed, there is a 62.5% chance they are liv<strong>in</strong>g at or below the<br />

poverty level. We would probably expect this figure to be quite high.<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 113

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