Question 356183
<pre>
 x      P(x)    x*P(x) (x-&#956;)^2*P(x)    
-----------------------------------   
 3	0.04	0.12	1.774224
 6	0.18	1.08	2.411208
 9	0.36	3.24	0.156816
12	0.36	4.32	1.971216
15	0.06	0.90	1.710936
             
</pre>



{{{mu=sum(x*P(x),i=1,5)=3(0.04)+6(0.18)+9(0.36)+12(0.36)+15(0.06)=9.66}}}
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{{{VAR=sum((x-mu)^2*P(x),i=1,5)=8.02}}}
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{{{sigma=sqrt(VAR)=2.83}}}