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# Probilities and stat watch

1. hi my friends, i'm really stuck at these 2 questions, which anyone please give me some hints on them?

for question c, i am complete clueless...

for question 8, i know the total area should equal to one. so if i let the area of P(X<80-a) be x, so the area of a and b should be x+2x=1-0.5239
so x=0.1587
and i'm stuck from there...

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2. For c

similar for P(X=1)

P(X=0)+P(X=1)=1.
3. (Original post by BabyMaths)
For c

similar for P(X=1)

P(X=0)+P(X=1)=1.
but why P(X=0)+P(X=1)=1 ?
does that mean if i define x=0,1,2 ; i have P(X=0)+P(X=1)+P(X=2)=1 ?
4. (Original post by kingsclub)
but why P(X=0)+P(X=1)=1 ?
because it should probably say

...for x=0, 1 and P(X=x)=0 otherwise.

X=0 and X=1 are the only possibilities.
5. (Original post by kingsclub)
hi my friends, i'm really stuck at these 2 questions, which anyone please give me some hints on them?

for question c, i am complete clueless...

for question 8, i know the total area should equal to one. so if i let the area of P(X<80-a) be x, so the area of a and b should be x+2x=1-0.5239
so x=0.1587
and i'm stuck from there...

FOr 8
SO you know

You get a/13 value from the standard distribution table ( )

2F(80-a)=P(X>80+b)=1-P(X<=80+b)=1-F(80+b)
and similarly to above

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