Stats doubt

[Granpa Simpson]

But Tsuki wen a ball is added wont Amita's set of elementary events change too...??

[Homer Simpson]

um..."set of elementary events"...meaning??  she did have 9 balls before and Amit adds a ball (green or red) - so she would actually have 10 now, right?

[Granpa Simpson]

Yes she will have 10 balls, thats the sample space, but now we dont know weder the transferred ball is green or red, if the transferred ball is red then the number of red balls will also increase and the probability will change and vice versa..!!!!

[Homer Simpson]

arrey lekin question is about both choosing different colored balls na...so Amit puts in green, she has to pick up red and vice-versa.

[Shefali]

Tsuki is ryt, ans is 7/15

[Granpa Simpson]

Gottit..thanx tsuki..:)

[Tanushree]

Thanks guys! tomorrow doing the papers! i am dead sure will get more to ask ...

[Tanushree]

I came across one normal disturbution problem. Which is giving me a big problem to solve it. Guys please Help

So the problem goes:

" A normal distribution has 77.0 as Mean. find Standard Deviation if 20% of the area under the curve lies to the right of 90.0"

It has even given a solution which I am facing little confusion

Ans: When X=90, Z= x-Mean / stand deviation = 90-77/SD=13/SD
P ( Z>z1)=0.20 ---------- P( 0=< Z=<z1)= 0.30 -------- z1= 0.84  ( this 0.84 it says it has come from the normal distrubuiton table.. But I cannot find it anywhere on the table..

I am confused " how did this 0.84 come from???)
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