An unbiased die is thrown twice. Let the event $A$ be 'odd number on the first throw' and $B$ the event 'odd number on the second throw '. Check the independence of the events $A$ and $B$.

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If all the $36$ elementary events of the experiment are considered to be equally likely, we have

$P(A)=\frac{18}{36}=\frac{1}{2}$ and  $P(B)=\frac{18}{36}=\frac{1}{2}$

Also         $P(A \cap B)=P($ odd number on both throws $)$

                $=\frac{9}{36}=\frac{1}{4}$

Now        $\mathrm{P}(\mathrm{A}) \mathrm{P}(\mathrm{B})=\frac{1}{2} \times \frac{1}{2}=\frac{1}{4}$

Clearly         $\mathrm{P}(\mathrm{A} \cap \mathrm{B})=\mathrm{P}(\mathrm{A}) \times \mathrm{P}(\mathrm{B})$

Thus,   $A$ and $B$ are independent events

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