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

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Density<br />

One question does rema<strong>in</strong>, however: what is the probability that the wait time is exactly<br />

2.5 m<strong>in</strong>utes<br />

The answer might not come as too much of a surprise: the probability is 0!<br />

The probability of a s<strong>in</strong>gle value <strong>in</strong> a cont<strong>in</strong>uous distribution is 0, s<strong>in</strong>ce there are <strong>in</strong>f<strong>in</strong>itely many<br />

possible values. Thus, 2.5 represents 1 of <strong>in</strong>f<strong>in</strong>itely many values. Take and you get 0!<br />

We can only f<strong>in</strong>d the probability of a non-zero range of values <strong>for</strong> a cont<strong>in</strong>uous random variable!<br />

Cont<strong>in</strong>uous Random Variables<br />

A cont<strong>in</strong>uous random variable is a random variable that has <strong>in</strong>f<strong>in</strong>itely many possible values<br />

with<strong>in</strong> a range of real numbers.<br />

As a result, the probability that a cont<strong>in</strong>uous random variable takes on any one specific value is<br />

0.<br />

Probability Density Function (PDF)<br />

The PDF of a cont<strong>in</strong>uous random variable is a cont<strong>in</strong>uous function such that the total area<br />

between the function and the horizontal axis is 1. The function‟s <strong>in</strong>put values are the values of<br />

the random variable, while the output values are densities. Densities are <strong>in</strong>dividually mean<strong>in</strong>gless<br />

values designed so that the total area equals 1.<br />

Reconsider the above wait-times example:<br />

0.25<br />

0.2<br />

0.15<br />

Time Spent 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 162

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