A bag contains 30 white balls and 10 red balls.

Question

A bag contains 30 white balls and 10 red balls. 16 balls are drawn one by one randomly from the bag with replacement. If X be the number of white balls drawn, then $$\left( {{{mean\,\,of\,X} \over {s\tan dard\,\,deviation\,\,of\,X}}} \right)$$   is equal to :

Accepted Answer

p (probability of getting white ball) = $${{30} \over {40}}$$

q = $${1 \over 4}$$ and n = 16

mean = np = 16.$${3 \over 4}$$ = 12

and standard diviation

= $$\sqrt {npq} $$ = $$\sqrt {16.{3 \over 4}.{1 \over 4}}  = \sqrt 3 $$

$$ \because $$ $$mean \over standard\,deviation$$ = $$12\over{\sqrt3}$$ = $$4{\sqrt3}$$

Solutions · 1