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

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Probability<br />

For <strong>in</strong>stance, we see that the probability that any 2 children <strong>in</strong> a classroom have the flu is 0.2.<br />

Let‟s call this random variable<br />

# of children <strong>in</strong> a classroom of 30 that have the flu.<br />

Then, we will write the probability that any 2 children have the flu as:<br />

( )<br />

This reads, “the probability that the number of children that have the flue is 2”<br />

The output of this statement is:<br />

( )<br />

What would it mean to say ask: What is ( )<br />

This is ask<strong>in</strong>g us to f<strong>in</strong>d the probability that 2 or fewer children have the flu. In other words,<br />

what is the probability that 0, 1, or 2 children have the flu. To answer this, we simply add the bar<br />

heights correspond<strong>in</strong>g to .<br />

( )<br />

Thus, there is a 74% chance that 2 or fewer children <strong>in</strong> a class of 30 children have the flu.<br />

With cont<strong>in</strong>uous distributions, we cannot simply read the “height of the bar!” For <strong>in</strong>stance<br />

consider the follow<strong>in</strong>g cont<strong>in</strong>uous probability distribution that shows the likelihood of various<br />

wait times <strong>in</strong> l<strong>in</strong>e at a fast-food restaurant:<br />

0.25<br />

0.2<br />

0.15<br />

Time Speng Wait<strong>in</strong>g <strong>in</strong> L<strong>in</strong>e<br />

0.1<br />

0.05<br />

0<br />

0 1 2 3 4 5<br />

M<strong>in</strong>utes<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 159

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