For a Binomial distribution, mean is \(15\) and variance is \(6\). If
\[
P(X\ge2)
=
1-\left(\frac25\right)^{25}k,
\]
then \(k=\)
Show Hint
For Binomial distribution:
\[
np=\text{Mean},
\qquad
npq=\text{Variance}.
\]
To calculate \(P(X\ge2)\), it is often easier to use the complement:
\[
P(X\ge2)=1-[P(X=0)+P(X=1)].
\]