1. The random variable X represents the number of persons in a Singapore family chosen at random and has the

following probability distribution:

Calculate:

(i) [1] The average family size in Singapore (do not round answer)

(a) 21

(b) 1.78

(c) 2.39

(d) 2.06

(ii) [1] The standard deviation of the number of persons in a Singapore family is

(a) 2.35

(b) 1.13

(c) 1.28

(d) 5.52

(iii) [1] In any randomly selected Singapore family, the probability that X is at most 3 is

(a) 0.22

(b) 0.11

(c) 0.89

(d) 0.78

(iv) [1] If a Singapore family has at most 3 persons, the probability that there are exactly 2 persons is

(a) 0.44

(b) 0.49

(c) 0.56

(d) 0.62

(v) [2] What is the probability that 2 randomly selected Singapore families will have at least 10 people in total?

(a) 0.0049

(b) 0.0021

(c) 0.0058

(d) 0.0037