UPSC NDA Math Model Paper 4

1. Here n = 18, n(X) = 2, n(S) = 6
p = n(X)/n(S) = 2/6 = 1/3
q = 1 - p = 1 - 1/3 = 2/3
Arithmatic mean of X = np
18× (1/3) = 6
2. Standard deviation =σ=√npq
=√18×

1

3

×

2

3

=√4
=2
Hence, option (3) is correct.