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

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Example 1:<br />

A fair-two sided co<strong>in</strong> is tossed 10 times. The goal is to get 8 heads.<br />

a) In how many different ways can this event occur<br />

b) Verify that all assumptions are met to conduct a b<strong>in</strong>omial experiment.<br />

c) What is the probability of this event<br />

SOLUTION:<br />

a) S<strong>in</strong>ce there are 10 events and 8 successes desired, there are:<br />

b)<br />

. /<br />

1) There are trials<br />

2) Each outcome is either a head (success) or a tail (failure)<br />

3) The probability of success on any trial is<br />

4) One toss does not <strong>in</strong>fluence the outcome of any other toss<br />

Thus, all assumptions have been met.<br />

c)<br />

( ) . / ( ) ( )<br />

Thus, there is about a 4.3% of toss<strong>in</strong>g 8 heads <strong>in</strong> 10 tosses.<br />

The fact that the probability of gett<strong>in</strong>g 8 heads <strong>in</strong> 10 tosses is higher than gett<strong>in</strong>g 9 heads <strong>in</strong> 10<br />

tosses should not surprise us. Gett<strong>in</strong>g 9 heads is a rather extreme request. Gett<strong>in</strong>g 8 heads, while<br />

still extreme, is a bit more likely.<br />

Let‟s now build the probability distribution histogram <strong>for</strong> . We first display the probabilities <strong>in</strong><br />

a table below by apply<strong>in</strong>g the b<strong>in</strong>omial pdf:<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 151

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