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

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1 st Bushel<br />

2 nd Bushel<br />

U1<br />

U1<br />

U2<br />

U2<br />

Perfect! So we see the rema<strong>in</strong><strong>in</strong>g two possibilities, right Well, actually, is there a difference<br />

between (U2, U1) and (U1, U2) Not unless those two bushels are actually different than one<br />

another! So, black<strong>in</strong>g out either one of these pairs leaves:<br />

1 st Bushel<br />

2 nd Bushel<br />

U1<br />

U1<br />

U2<br />

U2<br />

One possibility!<br />

You might be wonder<strong>in</strong>g why we‟re bother<strong>in</strong>g with this if we‟ve already found the probability.<br />

This is a good th<strong>in</strong>g to wonder.<br />

Recall that a probability is the number of ways an event can happen divided by the total number<br />

of outcomes. To be consistent with this def<strong>in</strong>ition, we really should be putt<strong>in</strong>g 1 <strong>in</strong> the<br />

numerator. Does that mean we miscomputed the probability Not <strong>in</strong> this particular example, but<br />

it can happen.<br />

To make our denom<strong>in</strong>ator consistent, let‟s look at the total number of possibilities <strong>for</strong> select<strong>in</strong>g<br />

bushels, add<strong>in</strong>g <strong>in</strong> the contam<strong>in</strong>ated bushel, C:<br />

1 st Bushel<br />

2 nd Bushel<br />

U1<br />

U1<br />

U2<br />

C<br />

U2 C<br />

Aga<strong>in</strong>, it is not possible to select the same pair twice, so we black-out the diagonals:<br />

1 st Bushel<br />

2 nd Bushel<br />

U1<br />

U1<br />

U2<br />

C<br />

U2 C<br />

Are we done Not unless we feel that (U2, U1) is different than (U1, U2). We notice that the<br />

three cells to the right of our blacked out diagonal are duplicates of those to the left. Thus we can<br />

cross them out, as well:<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 121

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