A lot consists of 20 defective and 80 non-defective items. Two items are drawn at random without replacement. What is the probability that both items are defective?
Two persons $A$ and $B$ take turns in throwing a pair of dice. The first person to throw $9$ from both dice will be awarded the prize. If $A$ throws first, then the probability that $B$ wins
If $P$ is the population proportion of some characteristic under study,
$Q=1-P$ and $n$ is the sample size, then the standard error of observed sample proportion is
If $A_i\ (i=1,2,\ldots,n)$ are $n$ independent events, with $P(A_i)=1-\frac{1}{2^i}$, then the probability that atleast one of the $n$ events occurs, is
Let $A$ be an event that a family has children of both sexes and $B$ be the event that the family has atmost one boy. If the family has $3$ children then the events $A$ and $B$ are
A fair coin is tossed $n$ times. Let the random variable $X$ denote the number of times the head occurs. If $P[X=1],\ P[X=2]$ and $P[X=3]$ are in arithmetic progression (AP), then the number $n$ of independent trial is