If 4,5,6,6,6,6,6,6,6,7 be a random sample from a poisson population with parameter λ, then an unbased estimate of λ is :

There are 35 students in a hostel. If the number of students increases by 7, the expenses of the hostel increases by Rs. 42 per day while the average
expenditure per head diminishes by Re. 1. The original expenditure of the hostel is:

 If 4,5,6,6,6,6,6,6,6,7 be a random sample from a Poisson population with parameter λ, then an unbiased estimate of λ is :

The coefficient of correlation between two variables X and Y is 0.48. The covariance is 36. The variance of X is 16. The standard deviation of Y is :

A random sample of size n is drawn from a population of size N by SRSWOR method. Then the standard error of sample mean will be zero if n is