I have trouble with this exercise:(adsbygoogle = window.adsbygoogle || []).push({});

I don't know how to do part b There are three boxes, each of them has 20 ICs and the i-th box has (4+i) ICs are defective.

a) From a box, take 1 IC. Let X be the number Ics are defective. Find the cumulative distribution funtion of X.

b) Choose a box randomly, then take 3 ICs . Let X be the number Ics are defective. Find the cumulative distribution funtion of X.

I think in part a:

Is that true? Could someone check it for me and explain how to do part b with 1st box:

F(X=0): 15/20

F(X=1): 15/20+5/20=1

with 2nd box:

F(X=0): 14/20

F(X=1): 14/20+6/20=1

with 3rd box:

F(X=0): 13/20

F(X=1): 13/20+7/20=1

thanks a lot!

:D

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# Homework Help: Finding the cumulative

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