The difference between mean and variance of a binomial distribution is 4 and the difference of their squares is 32. Then distribution is given by : |
$\left(\frac{1}{3}+\frac{2}{3}\right)^{36}$ $\left(\frac{1}{8}+\frac{7}{8}\right)^{36}$ $\left(\frac{1}{8}+\frac{7}{8}\right)^{8}$ $\left(\frac{1}{3}+\frac{2}{3}\right)^{9}$ |
$\left(\frac{1}{3}+\frac{2}{3}\right)^{9}$ |
$\text{Let mean}=m,\;\text{variance}=v.$ $m-v=4.$ $m^2-v^2=(m-v)(m+v)=32.$ $4(m+v)=32 \Rightarrow m+v=8.$ $m=6,\;v=2.$ $\text{For binomial distribution: }m=np,\;v=npq.$ $np=6,\;npq=2 \Rightarrow q=\frac{1}{3},\;p=\frac{2}{3}.$ $n=\frac{6}{2/3}=9.$ $\text{Distribution is }B(9,\frac{2}{3}).$ $\left(\frac{1}{3}+\frac{2}{3}\right)^{9}$ |